Self-sanitizing waveguiding surfaces

ABSTRACT

A self-sanitizing surface structure configured to selectively refract light, a method of fabricating a self-sanitizing surface configured to selectively refract light, and a method of decontaminating a surface using selectively refracted light. A waveguide including a support layer below a propagating layer is positioned over a substrate as a self-sanitizing layer. In the absence of a contaminant or residue on the waveguide, UV light injected into the propagating layer is constrained within the propagating layer due to total internal reflection. When a residue is present on the self-sanitizing surface structure, light may be selectively refracted at or near the interface with the residue along the side of the waveguide to destroy the residue. The self-sanitizing surface structure may be configured to refract a suitable amount of UV light in response to a particular type of residue or application.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/461,415 filed Feb. 21, 2017 and titledANTIBACTERIAL WAVEGUIDING SURFACES, the entire content of which isincorporated herein by reference.

FIELD

The present disclosure relates generally to antimicrobial andself-sanitizing surfaces, and more specifically to an apparatus and/orsurface structure that is cleaned with ultraviolet (UV) light.

BACKGROUND

Surfaces contaminated by pathogenic organisms such as bacteria, viruses,and/or fungi commonly act as vectors for the spread of such organismsbetween human hosts. Such contamination is a particular problem inhigh-traffic areas such as public bathrooms and facilities, foodpreparation environments such as factories and kitchens, shared vehiclessuch as transit, buses, rideshare, and taxis, and healthcareenvironments such as hospitals and ambulances, because theseenvironments often come into contact with large numbers of people,contain numerous surfaces that may be difficult to clean, and/or may berepeatedly exposed to substances containing elevated loads ofdisease-causing pathogens. Managing such surface contamination in orderto prevent or reduce cross-contamination and disease transmission is acrucial problem in public health. Accordingly, there is a need fortechnology that allows surfaces in such environments to be quickly andthoroughly sanitized.

One approach toward surfaces that can be thoroughly disinfected involvesthe use of antimicrobial chemicals on or within a surface. For example,coatings of silver (Ag) or quaternary ammonium polymers may be appliedas a thin layer over the top of a contamination-prone surface such as acounter or doorknob. The materials in the coating disrupt the cell wallsof any microbes that are in contact with the coating, thereby causingthese microbes to die. However, the time required for such coatings tokill microbes is often on the order of several hours. Furthermore, thecoatings wear off and lose efficacy over time, and must be periodicallyreplaced. Similarly, antimicrobial and disinfecting chemical cleaners(such as those including surfactants, ethanol, and/or bleach) wear offquickly and must be repeatedly topically applied.

Another approach toward surfaces that can be quickly disinfected is toutilize ultraviolet (UV) light. For example, a UV light source may bepermanently or temporarily suspended over a surface, such that UV lightmay be intermittently applied to that surface. When the UV light isincident on pathogens on that surface, the UV light induces oxidativedamage of genetic material and proteins within those pathogens, therebydisrupting crucial biochemical pathways and triggering pathogeninactivation and/or cell death. The utilization of UV light has asignificant advantage over antimicrobial coatings in its significantlyshorter timescale required for pathogen destruction (i.e., secondsinstead of hours). However, some frequencies of UV light can bedetrimental to human health, and thus, their use in environmentsfrequented by humans and other animals must be carefully controlled andmonitored. Moreover, the UV light source must have high power in orderto achieve an optical flux sufficient for killing microorganisms.Accordingly, improved strategies for managing surface contamination bypathogens are still needed.

SUMMARY

Aspects of embodiments of the present disclosure are directed toward aself-sanitizing surface structure (self-sanitizing waveguide surface), amethod of fabricating a self-sanitizing surface structure, and a methodof reducing contamination on a self-sanitizing surface structure.

Additional aspects will be set forth in part in the description whichfollows, and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to embodiments of the present disclosure, a self-sanitizingsurface structure may include a waveguide; the waveguide including: apropagating layer having a first transverse side and a second transverseside opposite the first transverse side, the first transverse side beingexposed to air and configured to selectively refract light; and asupport layer in direct contact with the second transverse side of thepropagating layer. The waveguide may be configured to selectivelyrefract about 0.01% to about 25% of the flux of an ultraviolet (UV)light injected into the propagating layer, the selective refractionoccurring when (for example, only when) a residue is on the firsttransverse side and at an interface with the residue.

The propagating layer in the self-sanitizing surface structure may beformed of amorphous silica, quartz, a metal fluoride, a fluoropolymer, acyclic ether-containing fluoropolymer, a PTFE-terpolymer,polychlorotrifluoroethylene (PCTFE), a cyclic olefin copolymer (COC),polymethylpentene, or zinc sulfide.

The propagating layer in the self-sanitizing surface structure may havea refractive index of about 1.3 to about 2.5.

The support layer in the self-sanitizing surface structure may include amirror or metallic layer.

The support layer in the self-sanitizing surface structure may have alower refractive index than the propagating layer.

The support layer in the self-sanitizing surface structure may include alayer of air, porous silica (silicon), or a low refractive index metalfluoride.

The self-sanitizing surface structure may further include: anultraviolet (UV) light source for generating UV light; and optics todirect the UV light into the propagating layer, the optics beingdirectly coupled to an end of the propagating layer perpendicular to thefirst and second transverse sides.

The UV light source in the self-sanitizing surface structure may be anexcimer lamp, a downshifting excimer lamp, an excimer laser, a lightemitting diode (LED), a mercury (Hg) vapor lamp, or a light sourcecomprising AlGaN quantum wells.

The UV light source in the self-sanitizing surface structure maygenerate UV-C light.

The optics included in the self-sanitizing surface structure may includecollimating optics, mirrors, refractive or reflective lenses,metamaterial-based lenses, Fresnel lenses, fibers, standard single modeoptical fibers, multimode optical fibers, photonic crystal opticalfibers, or a combination thereof.

The optics included in the self-sanitizing surface structure may bycoupled to the end of the propagating layer via a prism or grating.

The propagating layer in the self-sanitizing surface structure may notinclude any germicidal coating or layer on the first transverse side.

The self-sanitizing surface structure may further include a metalcoating on the first transverse side of the propagating layer, the metalcoating being configured to convert ultraviolet (UV)-C photons tosurface plasmon polaritons (SPPs).

The self-sanitizing surface structure may further include an opticalmirror on a terminating longitudinal side of the propagating layer.

The self-sanitizing surface structure may further include a structurallayer under the support layer.

The waveguide in the self-sanitizing surface structure may be configuredto support multimode waveguiding behavior.

The residue on the first transverse side of the waveguide may include anorganic compound, a microorganism, or a nucleic acid.

The self-sanitizing surface structure may further include: an additionalwaveguide adjacent to the waveguide, the additional waveguide includinga propagating layer; and parallel feeding optics or optics splitters todivide and inject the UV light into the propagating layers of thewaveguide and the additional waveguide.

According to embodiments of the present disclosure, a method offabricating the self-sanitizing surface structure of claim 1 mayinclude: attaching optical mirrors to a substrate, the optical mirrorshaving a height larger than that of the substrate; forming the supportlayer on the substrate between the optical mirrors; forming thepropagating layer by applying an ultraviolet (UV)-transparentpre-polymer coating on the support layer between the optical mirrors andcuring the UV-transparent pre-polymer coating; and coupling a UV lightsource to an injection end of the propagating layer.

According to embodiments of the present disclosure, a method of reducingcontamination on a self-sanitizing surface structure includes: selectinga wavelength of UV light and a light injection angle; selecting amaterial for a propagating layer and a material for a support layer;assembling the self-sanitizing surface structure from the selectedmaterial for the propagating layer and the selected material for thesupport layer to form a waveguide; and injecting UV light into thepropagating layer at the light injection angle to selectively refractabout 0.01% to about 25% of the flux of the UV light at a transverseside of the waveguide in the self-sanitizing surface, the selectiverefraction occurring when (for example, only when) a residue is on thewaveguide and at an interface with the residue.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of embodiments of the presentdisclosure will become more apparent by reference to the followingdetailed description when considered in conjunction with the followingdrawings, in which:

FIG. 1A is a schematic diagram showing the structure of a straight(planar) example channel waveguide 10 extending in the z direction andbeing guided along the x and y directions;

FIG. 1B is a schematic diagram showing the structure of a straight(planar) example slab waveguide 20 extending in the y and z directionsand being guided along the x direction;

FIG. 2A is a schematic diagram illustrating the reflection andrefraction of a ray of light at an interface between a first material(having a refractive index n₁) and a second material (having arefractive index n₂ smaller than that of the first material), asdescribed by Snell's law (Equation 2), n₁ sin θ_(i)=n₂ sin θ_(t);

FIG. 2B is a schematic diagram illustrating the refraction of a ray oflight at an interface between a first material (having a refractiveindex n₁) and a second material (having a refractive index n₂ smallerthan that of the first material) in the case where n₁, n₂, and the angleof incidence θ_(i) are selected so that the angle of transmission θ_(t)is 90°;

FIG. 2C is a schematic diagram illustrating total internal reflection(TIR) of a ray of light at the interface between the first material(having a refractive index n₁) and the second material (having arefractive index n₂ smaller than that of the first material) in the casewhere θ_(i) is equal to or greater than the critical angle θ_(c)(calculated as arcsin(n₂/n₁);

FIG. 3 is a schematic diagram illustrating injection of a light ray intoa waveguide with respect to the acceptance angle of the waveguide,followed by total internal reflection and transmission through thewaveguide;

FIG. 4 is a schematic diagram illustrating an example embodiment inwhich a residue on a surface of a waveguide and having a refractiveindex n_(con) larger than that of air (n₂=1.0) is exposed to lightrefracted at the surface of the waveguide due to changes in thecondition (θ_(c)=arcsin(n₂/n₁)) for total internal reflection;

FIG. 5 is a schematic diagram illustrating an example embodiment inwhich a residue on the surface of a waveguide is exposed to lightthrough the generation of an evanescent wave upon total internalreflection of light at the surface. The graph on the right side of thefigure shows the exponential decay in the intensity I of the evanescentwave (z-axis) with respect to the distance d from the surface (x-axis)and the continuity of this wave with the sinusoidal wave correspondingto the totally internally reflected light within the waveguide;

FIG. 6 is a schematic diagram illustrating the generation of a surfaceplasmonic position (SPP)-derived evanescent wave along an interfacebetween a metal layer and air when incident light transmitted through anunderlying translucent layer (e.g., the propagating material of awaveguide) is incident on the opposite side of the metal layer;

FIG. 7 is a block diagram describing the parts (including variousoptical components) and the movement of light through a self-sanitizingsurface structure according to embodiments of the present disclosure;

FIG. 8 is a table listing the dissociation energies (in eV) andultraviolet (UV) light wavelengths for dissociation (in nm) of somechemical bonds commonly found in organic and bioorganic residues,toxins, and chemical weapons, reproduced from Table 2.10 in Chapter 2 ofTsia, K. ed., Understanding Biophotonics: Fundamentals, Advances, andApplications, 2015, Taylor and Francis Group LLC, Boca Raton, Fla., theentire content of which is incorporated herein by reference;

FIG. 9 is a series of tables listing the chemical bond dissociationenergies (in kJ/mol) of selected phosphorus and nitrogen-containingchemical bonds, reproduced from the entry for “Bond DissociationEnergies” in Dean, J. A., Lange's Handbook of Chemistry, 15th ed., 1998,McGraw-Hill, New York, N.Y., the entire content of which is incorporatedherein by reference.

FIGS. 10A-10H are schematic diagrams showing various example embodimentsof optical components that may be connected to the propagating layer 105of a self-sanitizing surface structure. FIG. 10A shows an exampleembodiment of a self-sanitizing surface structure in which the opticsinclude a UV lamp (bulb), a mirror box surrounding the UV lamp, and afocusing lens. FIG. 10B shows an example embodiment of a self-sanitizingsurface structure in which the optics include the same optics as in FIG.10A, as well as a mirror on the terminal end of the propagating layer.FIG. 10C shows an example embodiment of a self-sanitizing surfacestructure in which the optics include a first focusing lens, and asecond focusing lens. FIG. 10D shows an example embodiment of aself-sanitizing surface structure in which the optics include a prism.FIG. 10E shows an example embodiment of a self-sanitizing surfacestructure in which the optics include a diffraction grating. FIG. 10Fshows an example embodiment of a self-sanitizing surface structure inwhich the optics include an LED laser with an integrated lens. FIGS. 10Gand 10H show an example embodiment of a self-sanitizing surfacestructure 170 in which the optics include a led laser 171 without anintegrated lens;

FIG. 11 is a schematic diagram illustrating the first four (lowestenergy) modes of the transverse component of a light wave undergoing TIRand propagation within a waveguide including cladding along the sidesperpendicular to the x-axis. The light waves are alternatingly of theform sin(θ) and cos(θ), where θ is constrained to mπ/d, d is thedistance between the sides of the waveguide, and m is an integer greaterthan or equal to 1. The energies associated with the light wave increasefrom left to right;

FIG. 12 is a schematic diagram showing a self-sanitizing surfacestructure including a UV lamp, a focusing lens, and a terminal endmirror as optical components, and a multi-layer structure including asubstrate layer, a support layer on the substrate layer, and apropagating layer on the substrate layer;

FIG. 13 is a flowchart summarizing the factors and acts included in themethod of decontaminating or reducing residue contamination on aself-sanitizing surface structure utilizing selectively refracted light;and

FIGS. 14A-B depict example rooms and surfaces, including an office and apublic lavatory, to which self-sanitizing surface structures accordingto embodiments of the present disclosure may be applied.

DETAILED DESCRIPTION

In the following detailed description, only certain example embodimentsof the subject matter of the present disclosure are shown and described,by way of illustration. As those skilled in the art would recognize, thesubject matter of the present disclosure may be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein.

In the context of the present application, when a first element isreferred to as being “on”, “coupled to”, or “connected to” a secondelement, it can be directly on, directly coupled to, or directlyconnected to the second element, or can be indirectly on, indirectlycoupled to, or indirectly connected to the second element with one ormore intervening elements interposed therebetween. Like referencenumerals designate like elements throughout the specification. Thethicknesses of layers, films, panels, regions, etc., may be exaggeratedin the drawings for clarity. The drawings are not necessarily drawn toscale.

As used herein, the terms “[to] clean”, “cleaning”, “[to]decontaminate”, “decontaminating”, and other verb form variationsthereof may refer to the partial or full removal or destruction ofsubstances that are harmful to human health, and more generally to theremoval or destruction of substances that have the potential to causeharm, loss, or inconvenience. While it will be understood that the scopeof such substances is not limited to any particular size, material, oramount, such cleaning and decontaminating action may be particularlyuseful for the removal of biologically and/or chemically harmfulsubstances or residues that are not visible to the unaided human eye dueto their particle size and/or amounts. Non-limiting examples of suchsubstances may include biological agents, such as viruses, bacteria,fungi, protozoa, and other pathogenic microorganisms; peptides,proteins, deoxyribonucleic acid (DNA), and other nucleic acid sequencesproduced by such microorganisms, as well as chemical agents, includingtoxins, poisons, irritants, substances used in chemical warfare, andexplosive materials. The terms may be used interchangeably with theterms “disinfecting”, “sanitizing”, “sterilizing”, etc., particularlywhen the substances to be removed include biological agents. The term“self-sanitizing” refers to an ability of a surface to routinely andinherently remove such substances in the absence of physical labor,including application of a secondary substance and/or physical laborsuch as scrubbing, wiping, etc.

As used herein, the terms “contaminant” or “residue” may refer to, forexample, any substance or material subject to removal or destructionduring decontamination by embodiments of the present disclosure,including the pathogenic, biological, and/or chemical agents describedabove.

As used herein, the term “light” is used in its art-recognized sense torefer to electromagnetic radiation having any wavelength. For example,although the term encompasses visible light (e.g., light having awavelength of 400-700 nm) as implied by the vernacular use of the term,it will be understood that references to “light” are not limited tovisible light, and expressly include electromagnetic radiation havingwavelengths outside of the visible range, including wavelengthscorresponding to gamma rays, X-rays, ultraviolet (UV) rays, infraredwaves, microwaves, radio waves, etc. Further, the term “light” may beused to refer to light including a single wavelength, as well as lightincluding a mixture or range of wavelengths. In some embodiments, theterm “light” may refer to electromagnetic radiation having a wavelengththat is selected for a specific purpose, for example, its efficacy interminating a specific organism or degrading a specific type of chemicalbond.

In some embodiments, the term “light” may be used to specifically referto ultraviolet (UV) radiation having a wavelength of 10 nm to 400 nm,including one or more wavelengths in the UV-A spectrum (e.g., about 315nm to about 400 nm), the UV-B spectrum (e.g., about 280 nm to about 315nm), the UV-C spectrum (e.g., about 200 nm to about 280 nm), and/or thevacuum UV (VUV) spectrum (e.g., about 10 nm to about 200 nm). In someembodiments, the term “light” may specifically refer to ultravioletradiation including one or more wavelengths in the UV-C spectrum.

Furthermore, due to the dual wave-particle nature of electromagneticradiation and light, it will be understood that although variousdescriptions of light herein may refer to “a ray”, “a wave”, “a photon”,etc., such terms may be used interchangeably, and the utilization of anyof these terms does not exclude the other terms, or models andformalisms using those terms.

As used herein, the terms “emit” and “emission” may be used to refer tolight or other electromagnetic radiation being generated by and releasedfrom a light source, such as a UV lamp. The terms “refract” and“refraction” may be used to refer to light being transmitted across aphase boundary (e.g., a boundary between phases including unlikematerials), and particularly to light exiting a surface or outerboundary of a waveguide, surface structure, or other structure that doesnot itself generate light, but is capable of internally transmittinglight and releasing that light across the boundary under selectedconditions. The term “transmit” and “transmission” may be used to referto light moving both through a material and across a boundary, and insome cases, the situations may be distinguished by referring to, forexample, “transmission through” or “within” a material and “transmissionat” or “across” a boundary. However, in some cases the terms may be usedinterchangeably, and it will be understood that those having ordinaryskill in the art are capable of distinguishing the origin and activityof the light according to context and the principles described herein.

The use of light (and particularly UV light) to kill microorganisms inthe art has typically involved the use of bulky UV light source fixturesabove the item or surface to be decontaminated. For example, such UVlight may be generated by a mercury lamp, excimer lamp, or LED (e.g.,UV-C LED) and transmitted through the air during application to the itemor surface. However, the UV light is not selective for pathogenicorganisms over other organisms, and the wavelengths and fluxes of UVlight commonly used for this purpose are also capable of causing skinand eye damage to humans, including short-term damage such as tissueburns, and long-term damage such as accelerated cell aging and DNAmutagenesis associated with development of cancer. As such, UV-assisteddecontamination has typically been limited to select environments withthe help of strict control measures.

Aspects of embodiments of the present disclosure are directed toward aself-sanitizing surface structure (self-sanitizing waveguide surface), amethod of fabricating a self-sanitizing surface structure, and a methodof reducing contamination on a self-sanitizing surface structure. Theself-sanitizing surface structure may be configured to selectivelyrefract light having a wavelength suitable for destroying or reducingthe concentration of residues on the self-sanitizing surface structure,and the method of reducing such contaminating residues may operate byselectively refracting light. Specifically, aspects of embodiments ofthe present disclosure are directed toward the utilization of awaveguide to guide, constrain, and selectively refract or transmit UVlight from within a surface structure under specific conditions (e.g.,only in the presence of a contaminating residue, and only at theinterface between the self-sanitizing surface structure andcontaminating residue), such that contamination can be reduced on theoutside of the surface structure with a decreased risk of human exposureto the UV light. Furthermore, some embodiments of the self-sanitizingsurface structure may prevent or limit refraction or transmission of UVlight from within the surface structure where the structure is in directcontact with a vacuum or gas (e.g., in areas of the surface whereresidue is not present and the surface is exposed to air and/or theenvironment adjacent to the structure).

The term “surface structure”, as used herein, may refer to a layer ofmaterial on or forming the outside or outermost part of an object. The“surface structure” may be a layer having a defined thickness andvolume, and in some embodiments, may be applied to or cover the outsideof an object made of materials different from those included in thesurface structure layer. For example, a conformal layer applied to theflat upper face of a countertop or the grasped portion of a roundeddoorknob may be referred to as a “surface structure”.

The term “surface”, when used without the following noun, is used in itsgeometrically understood sense to refer to the two-dimensional area ormanifold defining a boundary of a three-dimensional layer, object, orspace. Throughout this specification, planar areas corresponding tosurfaces of a surface structure may be distinguished from the surfacestructure itself by instead or additionally being referred to as “sides”(e.g., an upper side, a lower side) or “boundaries” (e.g., an upperboundary, a lower boundary) of the surface structure. Planar ortwo-dimensional areas corresponding to a boundary between two differentnamed materials may be additionally or specifically referred to as“interfaces”. When orientation and positional descriptors are used todistinguish between various sides of a surface structure (e.g., upperside, lower side, left side, right side), such descriptors may beinterpreted with reference to the example embodiments described in theaccompanying drawings. However, it will be understood that embodimentsof the present disclosure are not limited to the orientations depictedin the drawings. For example, although example embodiments may bedescribed herein as being oriented so that residues are deposited on andlight is refracted at an “upper side” with respect to the waveguideincluded in the self-sanitizing surface structure, the self-sanitizingsurface structure may be rotated or reoriented so that the “upper side”of the waveguide faces a different direction with respect to gravity.For example, while some drawings may depict a self-sanitizing surfacestructure attached to the upper-facing surface of a countertop,additional examples in which a self-sanitizing surface structure isattached to, e.g., the downward-facing surface of a ceiling or aside-facing surface of a wall are also included within the scope ofembodiments of the present disclosure.

The term “selectively refract”, as used herein, indicates that lightrefracted by the self-sanitizing surface structure is not continuouslyrefracted (i.e., not continuously released from the surface). Rather,the surface structure is designed and configured so that light isrefracted only under specific conditions and in a controlled manner withrespect to time and space. In some embodiments, the surface structuremay be configured so that light is substantially contained within thesurface structure under initial conditions (e.g., in air), but isrefracted outside of the structure only in the presence of a non-airresidue, for example, a residue having a refractive index higher thanthat of air. Furthermore, when light is refracted in the presence ofsuch a residue, light is refracted only at the portion of the surfacestructure that is directly adjacent to or in direct contact with theresidue. As such, the refraction of light is not uniform across thesurface structure, but instead exhibits spatial and temporal variationsbased on the specific configuration of the surface structure in contactwith the environment. Further, refraction can be automatically triggeredby environmental conditions, rather than requiring user monitoringand/or intervention.

As used herein, the term “waveguide” is used in its art-recognized senseto refer to a structure configured to guide or constrain thetransmission of waves (such as electromagnetic waves), such that thewaves propagate only within the space and along the direction traversedby the waveguide. In the absence of a waveguide, a wave propagates froma point source through open space (e.g., in all directions) as athree-dimensional (e.g., spherical) wave. Further, the power (i.e.,intensity) of the spherical wave decreases by a factor of 1/r² withincreasing radial distance r from the wave source, which can beunderstood as a decrease in flux density as the surface area of thespherical wavefront increases. However, a waveguide constrains wavesheld within that structure to propagate in a reduced number ofdimensions (i.e., one or two). As a result, the flux density in theplanar (two-dimensional) or one-dimensional wavefront decreases at amuch slower rate. In the case of a channel waveguide, the power of thewave ideally remains constant throughout propagation (e.g., assumingzero losses due to coupling and physical interactions such as scatteringwith and within the constituent materials).

When a wave is guided or constrained with respect to a particulardimension (direction), that dimension may be referred to as a “dimensionof guidance”.

The terms “channel structure waveguide” and “channel waveguide” may beinterchangeably used herein to refer to a waveguide in which a wave isguided (i.e., constrained) along two dimensions, and propagates freelyalong one dimension or direction (e.g., as a 1D wave). For example, achannel waveguide may be elongated in the z direction relative to the xand y directions. The structure or form of a channel waveguide may beunderstood by analogy to an aqueduct (i.e. a channel for water having alength much longer than its height and width). In a channel waveguide,the four transverse sides of the waveguide extend substantially parallelto the overall direction of wave propagation and the normal vectors ofthose sides are substantially perpendicular to the overall direction ofwave propagation. As used herein, the term “overall direction of wavepropagation” refers to the vector describing the overall movement(momentum) of a light wave transmitted directly down the center of thewaveguide.

The terms “slab waveguide”, “planar waveguide”, and “slab structurewaveguide”, etc., are interchangeably used to refer to a waveguide inwhich a wave is guided (e.g., constrained) along one dimension, andpropagates freely along two dimensions (e.g., as a 2D wave in a plane).For example, a slab waveguide may be elongated in the z and y directionsrelative to the x direction. In a slab waveguide, the two transversesides of a waveguide extend substantially parallel to the plane of wavepropagation and the normal vectors of those sides are perpendicular tothe plane or overall direction(s) of wave propagation.

In both types or kinds of waveguide structures, the longitudinal side(s)refers to the remaining, non-transverse sides of the waveguide. In someembodiments, the longitudinal sides of a waveguide are oriented withrespect to the transverse sides of the waveguide at an angle of 90°,such that those sides have normal vectors that are substantiallyparallel to the overall direction(s) of propagation. However,embodiments of the present disclosure are not limited thereto. In someembodiments, the longitudinal sides of the waveguide, channel waveguide,and/or slab waveguide may be sloped (e.g., may be oriented with respectto the transverse sides of the waveguide at an angle other than 90°,such that, for example, a cross-section of the waveguide has the shapeof a trapezoid, parallelogram, etc.). In some embodiments, thetransverse sides of the waveguide may be curved.

FIG. 1A is a schematic diagram showing the structure of a straight(planar) example channel waveguide 10 extending in the z direction andbeing guided along the x and y directions. The overall direction oflight wave propagation is substantially along the direction of the wavevector arrow 11. The four transverse sides 12, 14, 13, and 15 of thechannel waveguide 10 substantially extend along the z direction andalong the direction of wave propagation, and may also be defined bytheir normals, which are substantially perpendicular to the wave vectorarrow 11. The two longitudinal sides 16 and 17 of the channel waveguide10 may be defined as being substantially normal to the wave vector arrow11. Although the example channel waveguide 10 depicted in FIG. 1A issubstantially planar, embodiments of the present disclosure are notlimited thereto, as described below.

FIG. 1B is a schematic diagram showing the structure of a straight(planar) example slab waveguide 20 extending in the y and z directionsand being guided along the x direction. The overall direction of lightwave propagation is substantially along the direction of the two wavevector arrows 21 and 22 (e.g., as a 2D wave in the y-z plane). The twotransverse sides 23 and 24 of the slab waveguide 20 are substantiallyparallel to the y-z plane and have normals that are substantiallyperpendicular to the direction of wave propagation. The fourlongitudinal sides 25, 26, 27, and 28 of the slab waveguide 20 may bedefined as being parallel to the direction of wave propagation. Althoughthe example slab waveguide 20 depicted in FIG. 1B is substantiallyplanar, embodiments of the present disclosure are not limited thereto,as described below.

In some embodiments, the waveguide, channel waveguide, and/or slabwaveguide may be substantially flat or planar, as described above and/oras may be ascertained from the planarity of the transverse surfaces. Insome embodiments, at least some portions of the waveguide, channelwaveguide, and/or slab waveguide may be formed or bent to include acurvature or curved (non-planar) geometry, as may be ascertained fromthe non-planarity of the transverse surfaces. In these non-planarembodiments, a set of vectors describing the overall movement (momentum)of a light wave transmitted directly down the center of the waveguidemay vary in direction at different coordinates along the waveguide, butshould still describe a overall continuous field. As such, the terms“longitudinal sides” and “transverse sides”, in the context of curved ornon-planar waveguides, may still be used to identify or refer to thesurfaces of the waveguide when considered with respect to the localdirectionality of the vector field.

In some embodiments, the waveguides referred to herein may be dielectricwaveguides. The term “dielectric waveguide”, as used herein, refers to atype or kind of waveguide that is formed by combining alight-transmitting propagating layer with light-transmitting surroundingmaterials (described below), such that the surrounding materials areplaced along the dimensions of guidance. For example, a channelwaveguide may include a propagating layer that is substantiallyelongated in the z direction (with respect to the x and y directions),and is surrounded by the surrounding materials on its +x, −x, +y, and −ysides. A slab waveguide may include a propagating layer that issubstantially elongated in the z and y directions (with respect to the xdirection), and is surrounded by the surrounding materials on its +x and−x sides. The materials for the propagating layer and the surroundingmaterials may be selected in tandem, so that under specific conditionsdescribed herein, waves inserted into the propagating layer do not exitthe propagating layer at interfaces between the propagating layer andthe surrounding materials, but are instead reflected back into thepropagating layer.

Because the surrounding materials included in a dielectric waveguide arecapable of transmitting light, they can be described in terms of theirrefractive indexes. As used herein, the refractive index n (or index ofrefraction n) of a material is a dimensionless quantity that describesthe extent to which the phase velocity of light is changed as it passesthrough that material with respect to a reference material (herein, airat standardized pressure, having a normalized refractive index of 1.0).For example, the refractive index of a material corresponds to the ratioof the speed of light in the reference material vs. the speed of lightin the material of interest. As such, most refractive indexes aregreater than 1 (i.e., the phase velocity of light is reduced in mostmaterials). It will be understood that because the refractive index of amaterial varies according to the wavelength and frequency of light(which is the principle that causes light dispersion), the refractiveindexes used and described herein are to be considered “effectiverefractive indexes” for the particular wavelength or range ofwavelengths being used in the embodiment.

Residues on the surface of the waveguides included in self-sanitizingsurface structure embodiments of the present disclosure may beselectively exposed to light transmitted within the waveguide via one ormore mechanisms.

As a first exposure mechanism, in some embodiments, the residue may beexposed to light via refraction of light at the surface of thewaveguide. In general, when light is incident on a planar interfacebetween two materials having different refractive indexes, a portion ofthe light is reflected, and a portion of the light is transmitted orrefracted (bent) at that interface. Using approximations associated withgeometrical (ray) optics, the trajectory of the reflected portion can bedescribed according to Equation 1:θ_(i)=θ_(r)  Equation 1

where θ_(i) is the angle of incident light with respect to the vectornormal to that interface, and θ_(r) is the angle of reflected light withrespect to the vector normal to that interface.

Meanwhile, the trajectory of the refracted portion can be describedaccording to Snell's law (Equation 2):n ₁ sin θ_(i) =n ₂ sin θ_(t)  Equation 2

where n₁ is the refractive index of the first material (i.e., thematerial before the interface), n₂ is the refractive index of the secondmaterial (i.e., the material after the interface), θ_(i) is the angle ofincident light with respect to the vector normal (perpendicular) to thatinterface, and θ_(t) is the angle of transmitted light with respect tothe vector normal to that interface. When n₁>n₂, the resulting θ_(t) islarger than θ_(i) (i.e., the transmitted light is bent further away fromthe normal). FIG. 2A is a schematic diagram illustrating the reflectionand transmission (refraction) of a ray of light 31 at an interface 32between a first material 33 and a second material 34, specifically whenthe second material 34 has a refractive index smaller than that of thefirst material 33 and as described according to the variables inEquation 2. The relative amounts (i.e. intensities) of the transmitted(refracted) portion 37 and reflected portion 39 depend on thetransmission and reflection coefficients for the interface. It will beunderstood that those having ordinary skill in the art are capable ofcalculating these coefficients from the refractive indexes of the firstand second materials, if desired, but they are not crucial to theoperation of embodiments of the present disclosure. The angle betweenthe ray of light 31 and the normal to the interface is referred to asangle of incident light θ_(i) (35), while the angle between thetransmitted (refracted) ray of light 37 and the normal to the interfaceis referred to as angle of transmitted light θ_(t) (36).

For any given combination of n₁ and n₂ where n₁>n₂, there exists anangle of incident light θ_(i) at which the resulting angle oftransmitted light et will be π/2 (90°). At this angle, the light istransmitted parallel to the interface between the two materials. FIG. 2Bis a schematic diagram illustrating the refraction of a ray of light 31at an interface 32 between a first material 33 and a second material 34,specifically when n₁, n₂, and θ_(i) are selected so that θ_(t) (36) is90°. The angle of incident light θ_(i) (35) that satisfies thiscondition is known as the “critical angle” θ_(c) (39), and is denoted bythe dotted line 38. The critical angle may be further defined orcalculated as θ_(c)=arcsin(n₂/n₁).

When the angle of incident light θ_(i) (35) is equal to or larger thanthe critical angle θ_(c) (39) (i.e., θ_(c)≤θ_(i)<90°), the resultingangle of transmitted light θ_(t) (36) is greater than or equal to 90°from the normal vector (i.e., 90°≤θ_(t)<180°). As such, the transmittedlight is no longer transmitted and refracted past the interface of thetwo materials, but is instead reflected at the interface so that thelight remains in the first material. In this special case, because allof the light is reflected at the interface according to the geometricaloptics formalism, “total internal reflection” (TIR) is observed. FIG. 2Cis a schematic diagram illustrating the total internal reflection of aray of light 31 at an interface 32 between a first material 33 and asecond material 34, specifically when n₁>n₂ and θ_(i) (35) is equal toor greater than θ_(c) (39) (denoted by the dotted line 38). When theseconditions regarding the critical angle are found on two or more sidesof the waveguide, such that TIR occurs at each interface of thewaveguide, the wave may continue to propagate down the length of thewaveguide. In some embodiments, when the surrounding materials are solid(as opposed to being a liquid or gas), the materials may be referred toas “cladding” or a “cladding layer”.

As can be understood from the above discussion of critical angle, thebehavior of light within a waveguide is strongly dependent on thegeometry with which light is initially injected or inserted into thewaveguide. Accordingly, a waveguide may also be configured and describedin terms of its acceptance angle. As used herein, the term “acceptanceangle” is used in its art-recognized sense to refer to the largestangle, with respect to the core axis of the waveguide (e.g., the axisalong which light is propagated by the waveguide), at which light may beinjected into the waveguide and be subject to guidance, for example, viaTIR. The light may be injected into the waveguide at a longitudinal edgeof the waveguide that is not covered with a reflective material,cladding, etc. FIG. 3 is a schematic diagram illustrating injection of alight ray 31 into a waveguide 40 including a propagating layer 41surrounded by cladding 42 (including but not necessarily air) in the +xand −x directions. When the ray of light 31 is injected into thepropagating layer 41 along the z direction and at an angle equal to orsmaller than the acceptance angle 44, the ray 31 subsequently hits theinterface 45 between the propagating layer 41 and cladding 42 at anangle 35 equal to or larger than the critical angle 39 of thatinterface, such that the ray of light 31 is reflected back into thepropagating layer 41. As the ray of light 31 travels back and forthbetween opposite sides of the waveguide 40, the light continues to beincident on each interface at an angle larger than the critical angle,thereby remaining constrained within the propagating layer 41 whilebeing propagated in the z-direction. In contrast, a light ray that isinjected into the waveguide at an angle larger than the acceptance angle44 will not be reflected, and will leak out of the waveguide.

The acceptance angle θ_(ac) of a waveguide may be described orcalculated according to Equation 3:sin θ_(ac)=(n ₁ ² −n ₂ ²)^(1/2)  Equation 3

where θ_(ac) is the angle of light injection with respect to the axis ofwaveguide transmission (in FIG. 3, the z-axis), n₁ is the refractiveindex of the propagating material, and n₂ is the refractive index of thematerial surrounding the waveguide (e.g., cladding, liquid, or air). The“acceptance cone” circumscribed by the range of θ_(ac) rotated aroundthe normal defines the range of injection angles at which the light willbe constrained within the waveguide. As can be seen in Equation 3, thesize (e.g., angle) of the cone is a function of the refractive indexesof the propagating material and the cladding or surrounding material,with larger cones enabled by larger differences in refractive index.

The waveguide may be configured so that under normal conditions, i.e.,when the residue is not present, light propagating within the waveguideis contained within that structure (e.g., more than about 98%, 95%, 90%,80% or 70% of the light flux is contained and is not refracted ortransmitted through the surface of the waveguide). For example, therefractive index of the waveguide and the light injection angle may beselected as described in detail according to embodiments herein so thatlight propagating through the waveguide undergoes TIR when the residueis not present. When a residue is present on a surface of the waveguide,light may be refracted at the surface of the waveguide according to oneor more mechanisms described below.

In some embodiments, when the residue is capable of transmitting light(e.g., the residue includes or is suspended in a solvent such as water,as in the case of a microorganism, biofilm, sneeze droplets, etc.), adielectric interface different from that normally present in thewaveguide (e.g., between the waveguide and air) may be formed. As such,the critical angle for internal reflection will be changed at theresidue-waveguide interface. Specifically, when the residue has arefractive index higher than that of air (n=1.00), the critical anglefor internal reflection within the waveguide surface at that specificportion or area of the interface will be increased relative to theportions of the waveguide surface that remain in contact with air.

For example, when the propagating material of the waveguide has arefractive index n₁=1.40 and is in contact with air (n₂=1.00), thecritical angle θ_(c) for light in the waveguide material can becalculated using Snell's law (Equation 2) to be arcsin(1.00/1.40)=45.5°. Therefore, as described above, light incident on theair-waveguide interface will exhibit total internal reflection (TIR)when the angle of incidence θ_(i) is greater than or equal to 45.5°(e.g., θ_(i)≥45.5°). However, when a residue containing mostly water(n_(con)=1.33) is deposited on the surface, the critical angle at thepoint of deposition increases to arcsin(1.33/1.40)=71.8°, and lightincident on the air-waveguide interface will exhibit TIR only when theangle of incidence θ_(i) is greater than or equal to 71.8°. As such,light having an angle of incidence between 45.5° and 71.8° is trappedwithin the waveguide under clean or normal conditions (i.e., when thewaveguide is in contact with air), but is refracted when thewater-containing residue is present at the surface of the waveguide.Once refracted, the light can decontaminate the surface at the point ofcontact with the residue.

FIG. 4 is a schematic diagram illustrating an example of theabove-described working principle. A “countertop” waveguide surfacestructure 51 having a refractive index n₁ is placed in direct contactwith air (n₂<n₁) 52 in a first region 53 and with a water-containingresidue 55 (n₂<n_(con)<n₁) in a second region 57. A first ray of light59 incident on the interface 61 between the waveguide surface structure51 and air 52 undergoes total internal reflection in the first region53, while a second ray of light 63 having the same angle of incidence isrefracted at the interface 61 between the waveguide surface structure 51and residue 55 in the second region 57. Accordingly, light may becontained in the first region and selectively refracted in the secondregion without requiring any modification to the waveguide or input froman operator.

When a residue with a refractive index similar to or substantially equalto that of the waveguide (i.e., the propagating layer of the waveguide)is deposited on the surface structure (e.g., n_(con)≈n₁), the refractiveindex conditions for TIR are removed, and light is refracted at thesurface (transmitted past the interface) regardless of the angle ofincidence.

Changes in the ability of the waveguide to constrain light refractioncan also be described in terms of changes in the acceptance angle θ_(ac)(i.e., the geometry of light injection) rather than the critical angleθ_(c). Specifically, when a residue having a refractive index higherthan that of air (n=1.00) is present, θ_(ac) of the waveguide will bedecreased relative to the clean waveguide. For example, a cleanwaveguide with n₁=1.40 and n₂=1.00 (as used in the example above) can becalculated via Equation 3 to have an acceptance angle of arcsin[(1.96−1.00)^(0.5)]=78.5°. In comparison, a waveguide with a residuedeposited at any point along its side has a resulting acceptance angleof arcsin [(1.96−1.77)^(0.5)]=25.8°. As such, injected light having anacceptance angle between 25.8° to 78.5° is refracted at the point ofcontamination when a residue is present, but is constrained within thewaveguide at all other points and/or when no residues are present.

As a second exposure mechanism, in some embodiments, the residue may beexposed to light in the form of evanescent waves. As used herein, theterm “evanescent wave” may be used interchangeably with the term“surface wave” to refer to light that does not propagate sinusoidallythrough space (e.g., away from the surface) in the manner of other lightwaves or rays. Instead, the energy of the wave is concentrated within ashort distance from the surface of the waveguide. Such evanescent wavesare generated when the propagating light wave within the dielectricwaveguide exhibits TIR, and can be understood as a consequence of theboundary conditions expressed in Maxwell's equations, which requireelectromagnetic waves to be continuous across dielectric interfaces. Thefield strengths (e.g., intensities) of such evanescent waves decrease(or decay) exponentially with increasing distance from the surface, suchthat the risk of unwanted exposure to the light also decreases to zerowith increasing distance from the surface.

The evanescent waves may have a decay length or penetration distance(e.g., may extend from the surface to a distance) substantiallyequivalent to its 1/e roll-off point. The penetration distance d may becalculated according to Equation 4:d=λ ₀/2πn ₁[sin²θ₁−(n ₂ /n ₁)²]^(−1/2)  Equation 4

wherein λ₀ refers to the wavelength of transmitted light, n₁ and n₂refer to the refractive indexes of the waveguide and the surroundingmaterial, respectively, and θ₁ refers to the angle of incident light, asabove. Equation 4 thus quantifies the relationship between theevanescent wave penetration distance and those variables, anddemonstrates that the penetration distance may be tuned by selectingappropriate parameters.

For example, in a waveguide having n₁=2.0 that is in contact with aresidue having n_(con)=1.5 but otherwise surrounded by air (n_(air)=1.0)may be calculated using Equation 2 to have a critical angle θ_(c)=30°under clean conditions (i.e., when in contact with air) and θ_(c)=48.6°under contaminated conditions (i.e., in the presence of the residue).Therefore, light having an incident angle of, for example, θ_(i)=52°should undergo TIR and produce evanescent waves under both conditions.The penetration distance of evanescent waves generated by light havingan incident angle θ_(i)=52° and a UV-C wavelength of 220 nm may becalculated using Equation 4 to extend about 28 nm from the surface whenno residue is present at the waveguide surface, and to extend about 72nm from the surface of the waveguide when a residue is present on thewaveguide surface. Residues within this larger range of 0 to 72 nm(e.g., residues directly touching the surface) are affected by thelight, but any objects positioned outside this range are not affected.As the angle of incident light approaches the critical angle, thepenetration depth of the evanescent wave rapidly approaches a distanceon the order of a single wavelength (e.g., 220 nm in this example), andwhen the incident light is equal to the critical angle, the penetrationdepth goes to infinity and light is refracted at the surface.Accordingly, the penetration depth of the evanescent wave can beconfigured by selecting a suitable combination of light wavelength,incident angle, and material refractive indexes. The evanescent wavesmay propagate along the transverse sides of the waveguide (e.g.,parallel to the light propagating within the waveguide) for shortdistances.

FIG. 5 is a schematic diagram illustrating the generation of anevanescent wave 71 along the side of a waveguide 51 in contact with air52 in a first region 53, and in contact with a residue 55 in a secondregion 57. The evanescent wave 71 is generated upon total internalreflection (TIR) of a ray of light 59 at the interface between thewaveguide 51 and air 52 in the first region 53, and moves horizontally(e.g., along the z-direction) with respect to the surface of thewaveguide 51. The graph 73 on the right side of the figure shows theexponential decay in the intensity I of the evanescent wave 71 (z-axis)with respect to the distance d from the surface (x-axis), along with thesinusoidal wave 75 corresponding to the x-vector component of thetotally internally reflected light within the waveguide 51. The wave isobserved to be continuous at the interface between the waveguide 51 andthe air 52.

In some embodiments, the waveguide may further include a layer of metalon the side exposed to the user. In this case, evanescent waves may bealternatively generated through the excitation of surface plasmonpolaritons (SPPs) at the air-metal interface upon excitation of themetal by light (e.g., a photon, such as a UV-C energy photon) having asuitable frequency and momentum. For example, arrays of aluminumnanoparticles have been observed to exhibit plasmon resonances as low as215 nm (5.8 eV), as described in Maidecchi, et. al. ACS Nano, 7,5834-5841 (2013), the entire content of which is incorporated herein byreference.

FIG. 6 is a schematic diagram illustrating the generation of anevanescent wave 71 along a metal layer 81 in air 52 when a photon (rayof incident light) 59 is transmitted through an underlying translucentlayer 83 (e.g., the propagating material of a waveguide surface) and isincident on the opposite side of the metal layer 81. However,embodiments of the present disclosure are not limited thereto, and otherconfigurations and combinations of parts suitable for producing SPPevanescent waves may be used. For example, various configurations forand methods of producing SPPs are described in Ye, F. et al,Nanophotonics, 3(1-2), 44-39 (2014), the entire content of which isincorporated herein by reference, and it will be understood that thosehaving ordinary skill in the art are capable of integrating suchconfigurations and methods with the surface structures described herein.

As a third exposure mechanism, residues on a waveguide surface may beexposed to light by scattering. In some embodiments, when a residue onthe waveguide surface structure is larger (e.g., in scale or diameter)than the wavelength of the light propagated within the waveguide, anylight transmitted at the surface (for example, light in the form ofevanescent waves or refracted light due to a higher index of refraction)can be scattered to other residues on the surface via diffusescattering. Such scattering occurs in all directions, and may releaselight at an intensity of about 0.25 to about 5 mW/cm², or about 0.25 toabout 10 mW/cm². In some embodiments, the intensity ratio of scatteredlight in areas including such “large” residues compared to areas notincluding residues may be about 10 to about 100 times, or about 100 toabout 1000 times as strong.

The mechanisms for refracting or transmitting UV light may operatesequentially or simultaneously. The self-sanitizing surface structuresdescribed in example embodiments of the present disclosure may beconfigured to emit light according to any one or any combination of theabove described mechanisms. Furthermore, the specific mechanism orcombination of mechanisms, the amount (flux) of light transmitted intothe residue, and the specific conditions under which light istransmitted into the residue can be configured by selecting a suitablecombination of incident angle, acceptance and/or injection angle,refractive index, and/or material geometry, in accordance with theprinciples described above.

Aspects of embodiments of the present disclosure provide aself-sanitizing surface structure. The self-sanitizing surface structuremay include a waveguide, and the waveguide may include a propagatinglayer and a support layer. A first transverse side of the propagatinglayer (i.e., the side exposed to the user, or the upper side in thedrawings) may be exposed to air and be configured to selectively refractlight as described herein according to embodiments of the presentdisclosure, and a second transverse side of the propagating layeropposite the first transverse side may be in direct contact with thesupport layer. The propagating layer serves as a light propagatingmedium and may be alternatively referred to as the “core” of thewaveguide. The support layer may be configured to reflect light asdescribed herein according to embodiments of the present disclosure sothat light within the propagating layer is not transmitted into orabsorbed by any structures beneath it, and may also be referred to ascladding.

The material for forming the propagating layer should be transparent ormostly transparent to the wavelengths of light to be used within theself-sanitizing surface structure. As used herein, the term“transparent” may be used interchangeably with the term “opticallytransparent” to refer to a material capable of transmitting lightwithout absorbing or scattering it. The term “mostly transparent” mayrefer to a structure than allows passage of at least about 85% of theincident light, for example at least about 90% of the incident light, orin some embodiments, about 99% of the incident light per cm travelled inthe material. It will be understood that when a material is described asbeing “transparent”, the material is transparent to at least thewavelength or wavelengths of interest, but may not be transparent tolight of other wavelengths, and those having ordinary skill in the artare capable of determining which wavelengths are of interest accordingto the context and principles described herein.

The material for forming the propagating layer may be substantiallyamorphous (e.g., non-crystalline) to prevent or reduce scattering oflight within the waveguide. The amorphousness of a material can bequantified using X-ray diffraction (XRD); amorphous materials do notexhibit any XRD peaks.

In some embodiments, the propagating layer may be formed of an inorganicmaterial. Non-limiting examples of inorganic materials used to form thepropagating layer may include UV grade amorphous silica (such asCorning® HPFS® 7979 or 7980 (Corning, Corning, N.Y.), quartz glass, ametal sulfide (such as zinc sulfide (ZnS)), and metal fluorides (such asMgF₂, exhibiting >95-100% transmission at 220 nm). In some embodiments,the propagating layer may be formed of amorphous silica, which has theadvantage of being cheaper than quartz.

In some embodiments, the propagating layer may be formed of an organicfluoropolymer. Non-limiting examples of fluoropolymers used to form thepropagating layer may include a cyclic ether-containing fluoropolymersuch as CYTOP® Type S (AGC Chemicals, Tokyo, Japan) (exhibiting 93-95%transmission at 220 nm), a PTFE-terpolymer such as Solaflon® (POM TV UG,Cologne, Germany) (exhibiting 85% transmission at 220 nm),polychlorotrifluoroethylene (PCTFE, also known commercially as Kel-F®(3M, Maplewood, Minn.), Clarus® (Honeywell, Morris Plains, N.J.), andNeoflon® (Daikin, Osaka, Japan)) (exhibiting 90% transmission at 220nm), a cyclic olefin copolymer (COC) such as TOPAS® 8007X10 (TOPASAdvanced Polymers, Frankfurt, Germany) (exhibiting 70% transmission at280 nm), and polymethylpentene (PMP) (also known commercially as TPX™(Mitsui Chemicals, Tokyo, Japan)) (grade RT18 exhibiting 70%transmission at 300 nm). In some embodiments, the waveguide surface maybe formed of a cyclic ether-containing fluoropolymer such as CYTOP®and/or a PTFE-terpolymer such as Solaflon®.

In some embodiments, the propagating layer may be formed of a saturatedhydrocarbon or aliphatic polymer. Non-limiting examples of hydrocarbonor aliphatic polymers used to form the propagating layer may includepolystyrene (PS), polyvinyl chloride (PVC), and polymethyl methacrylate(PMMA).

The propagating layer is formed of a material having a refractive indexlarger than that of air (i.e., n>1.00). In some embodiments, thepropagating layer may be formed of a material having a refractive indexn of about 1.3 to about 2.5, for example, about 1.0 to about 2.0, about1.2 to about 1.8, or about 1.3 to about 1.7.

The materials for forming the propagating layer may be treated in orderto adjust or select a particular refractive index using any availablemethod in the art. In some embodiments, for example, the materials maybe subjected to mechanical stress and/or doped with impurities. In someembodiments, when the propagating layer is formed of a polymer, thepolymer may be modified with additional moieties to adjust therefractive index. However, embodiments of the present disclosure are notlimited thereto, and it will be understood that those having ordinaryskill in the art are capable of selecting suitable materials,treatments, and treatment methods according to the desired properties ofthe propagating layer.

In some embodiments, the propagating layer forms the uppermost layer ofthe self-sanitizing surface structure, and as such, the propagatinglayer is largely in contact with air (n=1.00) on the side exposed tousers. As such, when no residues are present on the surface of thewaveguide and light is propagated within the waveguide, the light isincident against and reflected by the air-waveguide interface due to thehigher refractive index of the propagating material (i.e., due to TIR,as described above). Further, when a residue is deposited on the top ofthe waveguide (i.e., the side exposed to users), the residue isdeposited directly on the propagating layer. As such, the air-waveguideinterface is replaced with a residue-waveguide interface at the point orarea of deposition.

As described herein, when a residue-waveguide interface is formed on thesurface of the waveguide, the critical angle for TIR within thewaveguide at the point of contamination is changed (i.e., decreased),such that one or more wavelengths of light that were previouslyconstrained within the waveguide may now be refracted at theresidue-waveguide interface. The amount of light that may be refractedupon this change (e.g., the range of light having an angle of incidencelarger than the critical angle at the air-waveguide interface, butsmaller than the critical angle at the residue-waveguide interface)depends on the combination of residues, the ambient environment, and thematerials for the propagating layer and other waveguide components. Assuch, the amount of light refracted at the surface of the waveguide maybe controlled or selected by using a suitable injection angle (e.g., aninjection angle that results in TIR in the absence of residue andrefraction in the presence of residue, as described herein according toembodiments of the present disclosure) and a suitable combination ofmaterials (e.g., a combination of refraction indexes that supports theTIR and refractive behavior as described above). In addition, theresidue deposited on the waveguide may be further exposed to transmittedlight via propagation of evanescent waves or by scattering, as describedherein.

The propagating layer may have a layer thickness (e.g., between the airand the support layer) of about 0.1 mm to about 4 mm, for example, about0.2 mm to about 3 mm, about 0.3 mm to about 2 mm, or about 0.4 mm toabout 1 mm. The width and length of the propagating layer are notparticularly limited.

The support layer is positioned directly adjacent to the secondtransverse side of the propagating layer, opposite the first transverseside exposed to the user. As described above, the support layer isselected so that light within the propagating layer is not transmittedinto or absorbed by any structures beneath it. Further, the supportlayer is selected so that light within the propagating layer isreflected back into and remains within that layer when light is incidenton the interface between the propagating layer and support layer.

In some embodiments, the support layer may include a layer that acts asan optical mirror. For example, the support layer may include a metal ormetallic layer, coating, or structure that acts as a reflective mirror.Non-limiting examples of metals that may be included in the supportlayer may include, for example, silver (Ag), nickel (Ni), and/oraluminum (Al). When the support layer includes a metallic layer, thelayer may be provided as a foil or a sheet that is attached by bondingto the second transverse side (i.e., lower side) of the propagatinglayer, or may be deposited on the propagating layer by, for example,spraying or evaporating.

In some embodiments, the support layer may include a layer that acts asa diffuse reflector, such as those made of porouspolytetrafluoroethylene (PTFE) or porous silica (silicon). When thesupport layer includes a diffuse reflector layer, the layer may beprovided as a sheet that is attached by bonding to the second transverseside (i.e., lower side) of the propagating layer.

In some embodiments, the support layer may include a transparent solidmaterial having a refractive index lower than the refractive index ofthe propagating layer, such that a dielectric interface is formed. Thetransparent solid material may be any material having a suitablerefractive index, as described herein, and for example, may be a lowrefractive index metal fluoride. Under the refractive index and criticalangle conditions described herein with respect to Equation 2, lightpropagating within the propagating layer should exhibit total internalreflection at the boundary between the propagating layer and the supportlayer. As such, the support layer may be referred to as cladding on thesecond transverse side of the propagating layer.

In some embodiments, the support layer may include a layer of gas, suchas air. For example, when the propagating layer is rigid enough toresist sagging and bending, the propagating layer may be suspended overa volume of air using one or more spacers. The spacers should be formedof a material that does not absorb light and is reflective or has arefractive index lower than the refractive index of the propagatinglayer.

The thickness of the support layer is not particularly limited as longas it is suitable for preventing or reducing light emission. In someembodiments, when the support layer forms a dielectric interface, thesupport layer may have a thickness of about 10 micron to about 1 cm, forexample, about 100 micron to about 0.5 cm. In some embodiments, when thesupport layer is formed of a metal, the support layer may have athickness of less than 1 mm, for example about 100 nm to about 100micron, or 150 nm to 10 micron. The width and length of the supportlayer are not particularly limited as long as the support layer has thesame or a larger footprint than the propagating layer.

In some embodiments, the self-sanitizing surface structure may furtherinclude a structural layer under the support layer. The structural layermay provide further structural support to the self-sanitizing surfacestructure, for example, to prevent or reduce sagging or bending when thepropagating layer and support layer have thicknesses that are liable tosuch distortions. The thickness, width, and length of the structurallayer are not particularly limited as long as they meet or supplementthe requirements described herein for the support layer.

In some embodiments, the self-sanitizing surface structure may furtherinclude a UV light source. In some embodiments, for example, when the UVlight source generates or spreads light in multiple directions (e.g., atmultiple angles), the UV light source may be coupled to the propagatinglayer via optics (i.e., optical components) so that UV light generatedby the UV light source can be injected into the propagating layer at asuitable angle (e.g., an injection angle that results in TIR in theabsence of residue and refraction in the presence of residue, asdescribed herein according to embodiments of the present disclosure).

FIG. 7 is a block diagram 90 describing the parts (including variousoptical components) and the movement of light through a self-sanitizingsurface structure according to embodiments of the present disclosure. AUV light source 91 provides light to transmitting and/or focusing optics93 so that the light is injected into a waveguide propagating layer 95.If a residue is present on the waveguide propagating layer 95,refraction 97 of a portion of the light occurs at the location of theresidue. The remaining portion of the light remains in the waveguidepropagating layer 95, and may be reflected by a mirror 99 positioned atthe terminal end of the waveguide propagating layer 95, so that thelight remains within the waveguide propagating layer 95 instead ofexiting the layer.

The UV light source may be selected to produce light having one or morewavelengths of interest at a suitable intensity for surfacedecontamination. In some embodiments, the UV light source may producemultiple wavelengths and/or a wide range of wavelengths, but be filteredto restrict the range of emitted wavelengths to a narrower sub-range orspecific wavelengths.

In some embodiments, the UV light source may be selected to produceUV-A, UV-B, and/or UV-C light. In some embodiments, for example inbiodecontamination applications, the UV light source may preferablyproduce UV-C light (e.g., light having wavelengths of about 200 nm toabout 280 nm or about 200 nm to about 290 nm), but embodiments of thepresent disclosure are not limited thereto. UV-C light is known to havegermicidal effects and is not able to penetrate past the upper deadlayer of human skin despite its higher energy, due to increasedabsorption and scattering of light in this wavelength range bybiomolecules located in this layer of skin. The use of UV-C light forgermicidal purposes as applied using a KrBr excimer lamp and transmittedthrough air is described in, for example, Buonanno et al., “207-nm UVLight—A Promising Tool for Safe Low-Cost Reduction of Surgical SiteInfections. I: In Vitro Studies”, PLOS One, October 2013, 8(10), e76968,the entire content of which is incorporated herein by reference.

The UV light refracted at the surface of the self-sanitizing surfacestructure may be selected to target one of more types or kinds ofbiological residues. For example, UV light having a wavelength of lessthan or equal to about 250 nm has an energy suitable for breaking thechemical bonds of amino acids, thus denaturing essential proteins. UVlight having a wavelength of greater than or equal to about 250 nm hasan energy suitable for breaking nucleic acids such as DNA and RNA, whichcan trigger apoptosis, necrosis and/or lysis in cells, or inactivate avirus. The terms “apoptosis” and “necrosis” are used in theirart-recognized sense to refer to any suitable mechanism of programmed orsudden premature cell death, including mechanisms that result in geneticmaterial degradation and membrane disruption. The terms “lysis” and“lyse” are used in their art-recognized sense to refer to disruption orbreakage of a cell's membrane with concomitant release of its contents,thereby resulting in cell death.

In some embodiments, the UV light refracted at the surface of theself-sanitizing surface structure may be selected to target chemicalresidues. Many organic bonds included in residues such as toxins,chemical weapons, and explosive residues have bond dissociation energiesthat match the energy available from UV light. For example, many toxins,chemical weapons, and explosive compounds include one or morecarbon-nitrogen (C—N), carbon-phosphorus (C—P), and/or carbon-carbon(C—C) bonds. When UV light having an energy equal to or greater than thedissociation energy of a bond is applied to the molecule, the bond maybe broken and the activity of the organic compound may be destroyed.FIG. 8 includes a list of various chemical bonds, their dissociationenergies, and the corresponding wavelength of UV light required toinitiate bond dissociation. The data in FIG. 8 is reproduced from Table2.10 in Tsia, K. ed., Understanding Biophotonics: Fundamentals,Advances, and Applications, 2015, Taylor and Francis Group LLC, BocaRaton, Fla., the entire content of which is incorporated herein byreference. Additional bond types and energies can be found in otherreferences in the art, such as Dean, J. A., Lange's Handbook ofChemistry, 15th ed., 1998, McGraw-Hill, New York, N.Y., the entirecontent of which is incorporated herein by reference.

References listing chemical bond dissociation energies in kJ/mol can beconverted to the corresponding UV light wavelength according to Equation5:λ=h*c/E=h*c/{[dissociation energy(in kJ/mol)]/N _(A)}  Equation 5

where c is the speed of light (2.998*10⁸ m s⁻¹), h is Planck's constant(6.6260755*10⁻³⁴ J S), and N_(A) is Avogadro's constant (6.022*10⁻²³units mol⁻¹). For example, a bond dissociation energy of 598 kJ/molcorresponds to 200 nm UV light, and a bond dissociation energy of 342kJ/mol corresponds to 350 nm UV light.

FIG. 9 is a chart providing additional examples of the energies forphosphorus- and nitrogen-containing bonds in kJ/mol, reproduced fromTable 4.11 (“Bond Dissociation Energies”) from Dean, J. A., Lange'sHandbook of Chemistry, 15th ed., 1998, McGraw-Hill, New York, N.Y.

The example materials described herein for forming the propagating layerare typically more transparent as the wavelength of light is increased.In some embodiments, this may be due to a lesser degree of absorption bychemical bonds within the material. Accordingly, the wavelength of lightmay be changed or selected in order to achieve better optical propertieswith respect to a particular waveguide material, although thesuitability of the wavelength for decontamination should also be afactor for consideration.

In some embodiments, the UV light source may include a single lamp. Insome embodiments, the UV light source may include multiple lamps.Non-limiting examples of suitable UV light sources may include excimerlamps (such as KrCl, which emits at 222 nm), downshifting excimer lamps(such as Xe₂, which emits at 172 nm and is downshifted with a phosphorto 220 nm to 290 nm), an excimer laser, a LED, a mercury (Hg) vapor lamp(which emits at 254 nm), and light sources including AlGaN quantumwells. In some embodiments, the UV light source may be a Hg vapor lampor an excimer tube lamp.

Non-limiting examples of optics (optical components) for coupling the UVlight source to the propagating layer may include collimating optics,mirrors, refractive lenses, reflective lenses, and optical fibers. Whenthe optics include lenses, non-limiting examples of such lenses mayinclude metamaterial-based lenses, Fresnel lenses, etc. Further, thelenses may be narrow-band lenses as long as they are suitably compatiblewith the wavelengths generated by the UV light source. When the opticsinclude optical fibers, the fibers may be standard single mode fibers,multimode fibers, hollow core or solid core photonic crystal fibers,etc. The optical fibers should be at least partially transmissive to UVlight, for example, at least about 50% transmissive, at least about 65%transmissive, or at least about 80% transmissive.

FIGS. 10A-10H are schematic diagrams showing various example embodimentsof optical components that may be connected to the propagating layer 105of a self-sanitizing surface structure having an upper transversesurface 111 containing a residue 109, a lower transverse surface 112, afirst longitudinal side 113, and a second longitudinal side (terminalend) 114.

FIG. 10A shows an example embodiment of a self-sanitizing surfacestructure 100 in which the optics include a UV light source (e.g., alamp or bulb) 101, a mirror box 107 surrounding the UV light source 101,and a focusing lens 103. The UV light source 101 is coupled to the firstlongitudinal side 113 of the propagating layer 105 via the focusing lens103 in order to inject the light 115 produced by the UV light source 101into the propagating layer 105 at a particular angle or set of angles(as described in detail according to embodiments of the presentdisclosure herein). The mirror box 107 traps light produced by the UVlight source 101 that may be directed away the self-sanitizing surfacestructure 100 and reflects said light toward the focusing lens 103 inorder to increase the efficiency or flux of light 115 that is injectedinto the propagating layer 105.

FIG. 10B shows an example embodiment of a self-sanitizing surfacestructure 120 in which the optics include a UV light source 101, amirror box 107 surrounding the UV light source 101, and a focusing lens103 as in FIG. 10A, as well as a mirror 117 on the terminal end 114 ofthe propagating layer 105. The mirror 117 reflects light 115 that wouldnormally refract and exit the propagating layer 105 at its terminal end114, thereby preventing or reducing loss of flux from the propagatinglayer 105 at that end. In addition, the UV light source 101 and focusinglens 103 are positioned at an angle less than 180° from the plane of theself-sanitizing surface structure 120 to thereby modify the injectionangle of the light 115. It will be understood that the particularposition of the UV lamp with respect to the self-sanitizing surfacestructure 120 is merely illustrative, and other positional angles ordistances may be selected according to the principles described herein.

FIG. 10C shows an example embodiment of a self-sanitizing surfacestructure 130 in which the optics include a UV light source 101, amirror box 107 surrounding the UV light source 101, a first focusinglens 103, and a second focusing lens 131. The UV light source 101 iscoupled to the first longitudinal side 113 of the propagating layer 105via the focusing lenses 103 and 131 in order to inject the light 115produced by the UV light source 101 into the propagating layer 105 at aparticular angle or set of angles (as described in detail according toembodiments of the present disclosure herein). It will be understoodthat the particular combination of biconvex lenses 103 and 131 shown inFIG. 10C is merely illustrative, and that other combinations, numbers,and types or kinds of lenses that may be suitably used to focus and/ordirect light into self-sanitizing surface structures according to theembodiments herein. The number of lenses is not particularly limited,and may be 1, 2, 3, 4, etc. Non-limiting examples of suitable kinds oflenses include biconvex, piano-convex, positive meniscus, negativemeniscus, plano-concave, and biconcave lenses, and may be used in anysuitable combination (e.g., a combination that results in injection oflight at an angle that enables selective refraction in the presence of aresidue, as described herein according to embodiments of the presentdisclosure).

In some embodiments, one or more optical components may be positioned sothat light is injected into the propagating layer at a longitudinal sideof the layer, for example, on a third side perpendicular to the firstand second transverse sides (e.g., side 113 of the propagating layer105, as shown in FIGS. 10A-C). For example, when the self-sanitizingsurface structure includes a channel structure waveguide that extends inthe z direction and is guided (limited) along the x and y directions,the optics may be coupled to a plane having a normal substantiallyparallel to ±z. The side of the propagating layer coupled to the UVlight source via the optics may be alternately referred to herein as thebeginning side, injection end, or injection side (referring to injectionof light), and the opposite or remaining sides may be referred to as theterminating side(s), terminating end(s) (referring to the end point ofthe propagated light), or non-injection side(s)) (e.g., side 114 asshown in FIGS. 10A-C).

In some embodiments, one or more optical components may be positioned sothat light is injected into the propagating layer at a transverse sideof the propagating layer (e.g., side 111 or 112 of the propagating layer105, as shown in FIGS. 10A-C). For example, when the self-sanitizingsurface structure includes a channel structure waveguide that is guidedalong the x and y directions and extends in the z direction, the opticsmay be coupled to a plane having a normal perpendicular to ±z. In someembodiments, for example when the optics include a prism or a grating,the optics may be positioned on the upper surface of the propagatinglayer.

FIG. 10D shows an example embodiment of a self-sanitizing surfacestructure 140 in which the optics include a UV light source 101, amirror box 107 surrounding the UV light source 101, a first focusinglens 103, a terminal end mirror 117, and a prism 141. The UV lightsource 101 is coupled to the propagating layer 105 via the focusing lens103 and the prism 141 in order to inject the light 115 produced by theUV light source 101 into the propagating layer 105 at a particular angleor set of angles (as described in detail according to embodiments of thepresent disclosure herein).

FIG. 10E shows an example embodiment of a self-sanitizing surfacestructure 150 in which the optics include a UV light source 101, amirror box 107 surrounding the UV light source 101, a first focusinglens 103, and a diffraction grating 151. The UV light source 101 iscoupled to the propagating layer 105 via the focusing lens 103 and thediffraction grating 151 in order to inject the light 115 produced by theUV light source 101 into the propagating layer 105 at a particular angleor set of angles (as described in detail according to embodiments of thepresent disclosure herein).

In some embodiments, when the UV light source is a LED, the LED mayinclude an integrated lens (e.g., a lens may be included or embedded inthe LED housing, for example, between the luminescent emission layer andthe irradiation target). In some embodiments, the LED with an integratedlens may be coupled to the propagating layer without the use of anyadditional and/or intermediate lenses. In some embodiments, the LED withan integrated lens may be coupled to the propagating layer by furtherutilizing one or more additional optical components as described above.

FIG. 10F shows an example embodiment of a self-sanitizing surfacestructure 160 in which the optics include an LED laser 161 with anintegrated lens 163. The laser light is focused and injected into theside 113 of the propagating layer 105 at a particular angle or set ofangles (as described in detail according to embodiments of the presentdisclosure herein). FIGS. 10G and 10H show an example embodiment of aself-sanitizing surface structure 170 in which the optics include a ledlaser 171 without an integrated lens. The laser light is directlyinjected into the side 113 of the propagating layer 105 at any suitableangle smaller than the acceptance angle 173, and may be rotated awayfrom 180°, as shown in FIG. 10G, to select an injection angle that mayenable selective refraction, as shown in FIG. 10H and as describedherein according to embodiments of the present disclosure.

In some embodiments, the propagating material may be coupled to the UVlight source via a prism or a grating positioned in contact with thesurface, where the prism or grating is configured to inject light intothe propagating material. The size, shape, and material of the prism isnot particularly limited. In some embodiments, when the propagatingmaterial is coupled to a grating, the grating may be etched into anexposed portion of the waveguide (e.g., a portion that is not covered bycladding). In some embodiments, the grating may be deposited as a thinfilm or layer on top of an exposed portion of the waveguide.

The UV light should be introduced (injected) into the self-sanitizingsurface structure at a suitable injection angle so that the resultingangle of incident light at the boundaries of the propagating layer islarger than the critical angle for a clean surface structure (e.g., incontact with air), but smaller than the critical angle for acontaminated surface structure (e.g., in contact with a residue, such asa microorganism containing water). When this condition is fulfilled, UVlight is constrained within the surface structure under normal (clean)conditions, but is refracted at the sides of the surface structure undercontaminated (residue) conditions until the residue is killed, removed,or degraded upon photoreaction with the light. As such, the amount oflight the waveguide may be controlled or selected by using a suitableinjection angle or range of injection angles, as determined by thecombination of materials and refraction indexes as described hereinaccording to embodiments of the present disclosure.

In some embodiments, for example, the UV light is injected into theself-sanitizing surface structure within the acceptance angle of thepropagating layer. In some embodiments, the UV light is injected intothe sanitizing surface structure at an angle that is within theacceptance angle of the propagating layer under clean conditions, butoutside of the acceptance angle of the propagating layer undercontaminated conditions.

In some embodiments, substantially all of the UV light is injected intothe self-sanitizing surface structure within the acceptance angle. Inother embodiments, a fraction of the UV light is injected into theself-sanitizing surface structure within the acceptance angle. In someembodiments, for example, about 10%, about 20%, about 30%, about 40%,about 50%, about 60%, about 70%, about 80%, or about 90%, of the UVlight is injected into the self-sanitizing surface structure within theacceptance angle. In some embodiments, about 20% to about 80%, about 30%to about 70%, or about 40% to about 60% of the UV light is injected intothe self-sanitizing surface structure within the acceptance angle.

In some embodiments, when UV light is used within the self-sanitizingsurface structure, decontamination, specifically decontamination ofbiological agents, may be achieved without the use of germicidalcoatings or layers.

In some embodiments, the self-sanitizing surface structure may furtherinclude a thin metal coating on the first transverse side of thepropagating layer (i.e., the side exposed to the user). In this case,residues are deposited on the metal coating, and photons transmittedfrom the propagating layer to the metal coating generate surface plasmonpolaritons (SPPs), as described above. The thin metal coating may haveany suitable thickness, for example, about 10 nm to about 500 nm. Insome embodiments, the metal coating may be deposited on the entire firsttransverse side of the propagating layer, or may be deposited on only aportion of the first transverse side of the propagating layer.

In some embodiments, the self-sanitizing surface structure may furtherinclude an optical mirror at a terminating longitudinal side of thepropagating layer. The optical mirror may be used to reflect light backinto the waveguide and to prevent or reduce light from being refractedat that boundary. The mirror may be planar or non-planar. In someembodiments, the optical mirror may be a thin sheet of film of a metal,such as aluminum, silver, or nickel. In some embodiments, the opticalmirror may be a diffuse reflector, such as those made of porouspolytetrafluoroethylene (PTFE). In some embodiments, when the waveguideis a slab or planar waveguide structure having four longitudinal sides,one of which is the injection end coupled to the UV light source viaoptics, an optical mirror may be positioned at one, two, or three of theremaining sides (e.g., terminating and/or longitudinal sides).

In some embodiments, the self-sanitizing surface structure may furtherinclude a mirror box (e.g., an enclosure having mirrored inside walls)around the UV light source, for example, to direct light produced by theUV light source into the propagating layer, or to prevent or reduceunwanted radiation loss from the UV light source. The dimensions,materials, etc. used to form the mirror box are not particularly limitedand may be suitably selected by those having ordinary skill in the artaccording to the principles described herein.

In some embodiments, the self-sanitizing surface structure may be formedover a substrate. For example, the substrate may be under the supportlayer. The substrate may have any arbitrary shape or topology, such asthat of a doorknob, counter surface, railing, etc. In some embodiments,the substrate may be at least part of a room fixture or furniture itemsuch as a table, counter, wall, floor, roof, ceiling, chair, toilet,etc., or may be part of a device or object such as a handle, grip, case,etc. In some embodiments, the self-sanitizing surface structure may beformed over the surface of a substrate formed of conventional materials(e.g., as a cover or top surface). In some embodiments, when thesubstrate is reflective or has a lower refractive index than thepropagating layer, the substrate may also function as a support layer,and can be used directly under the propagating layer of theself-sanitizing surface structure (e.g., without a support layer).

The self-sanitizing surface structure and its constituent parts may haveany suitable footprint and curvature, i.e., any curvature that allowsthe waveguide to prevent or constrain the refraction of light along thesurfaces of the waveguide when the waveguide is in contact with air, andto refract light when the waveguide is in contact with a residue havinga refractive index larger than that of air, for at least one set (range)of incident angles. The curvature may be uniform or non-uniform acrossthe footprint of the surface structure, and may be symmetric ornon-symmetric. In some embodiments, the self-sanitizing surfacestructure and its constituent parts may each have substantially nocurvature, such that they are substantially planar (flat). In someembodiments, the self-sanitizing surface structure and its constituentparts may each be non-planar so as to conform to a curved or non-planarunderlying surface. It will be understood that when at least one portionof the self-sanitizing surface structure has non-zero curvature, thegeometry of the interaction of light transmitted within the waveguidewith the surfaces of the waveguide (i.e., the angle of incidence) mayvary across the waveguide surface, such that it may become moredifficult to select a suitable combination of injection angle andmaterial. However, those having ordinary skill in the art are capable ofselecting such configurations according to the principles describedherein.

The self-sanitizing surface structure may be configured to refract asuitable amount of UV light in response to a particular type of residueor application. For example, the surface may be configured to refractabout 0.01% to about 25%, and in some embodiments, about 0.1% to about20%, about 1% to 10%, or about 2% to 5% of a UV light transmitted withinthe propagating layer (i.e., with respect to the total flux of the UVlight) when a residue is positioned on the first transverse side.Furthermore, the amount of UV light transmitted at the surface of theself-sanitizing surface structure may be tuned by selecting suitableparameters in order to favor one or more exposure mechanisms, asdescribed herein, for example, by changing the insertion angle of the UVlight.

As described above, the self-sanitizing surface structure may beconfigured to selectively refract light only when a residue is present,and at an interface with the residue. That is, light is not refractedindiscriminately along the entire surface of the self-sanitizing surfacestructure, and is refracted only in specific portions or regions of theself-sanitizing surface structure, under specific conditions. Fromanother perspective, the self-sanitizing surface structure may refractlight along less than 100% of the surface of the self-sanitizing surfacestructure, for example, less than about 70%, less than about 50%, lessthan about 40%, less than about 30%, less than about 20%, etc.

In some embodiments, the propagation of light within the waveguide maybe limited to one or more modes. The term “mode” is used herein in itsart-recognized sense to refer to a standing wave that is able to existwithin and propagate through the waveguide, and is “allowed” given theboundary conditions (geometry) of the waveguide. A mode also denotes asolution of the wavefunction describing the propagation of anelectromagnetic wave through a waveguide. A light wave that is injectedto the waveguide at an angle or frequency that does not match one of theallowed modes of the waveguide is unable to propagate through thewaveguide.

A light wave injected into a planar waveguide at a non-zero injectionangle bounces back and forth between opposing sides of the waveguide asit traverses the distance of the waveguide. The propagation of the lightwave thus includes multiple segments, the trajectory of each of whichcan be separated into a transverse component (for example, a vector inthe x direction) and a longitudinal component (for example, a vector inthe z direction). FIG. 11 is a schematic diagram illustrating the firstfour (lowest energy) modes (i.e., wavefunction solutions) of thetransverse component of a light wave 205 undergoing TIR and propagationwithin a waveguide 200 that is limited along a dimension (x) to have awidth d and is composed of a central propagating material 201 surroundedby cladding 203 (e.g., air) along the sides perpendicular to the x-axis.The light waves associated with each mode are alternatingly of cosineand sine form, where m is the index of the mode, 0 denoting thefundamental mode having 0 nodes (i.e., points of waveform cross-overwith the z-axis, where a larger number of nodes is correlated withhigher wave frequencies and energies). The energies associated with thelight wave increase from left to right as the index of the modeincreases. The “bleeding” of the sine and cosine waveforms beyond theinterface between the central propagating material 201 and the cladding203 is explained in more detail herein, in connection with thediscussion of evanescent waves.

From another perspective, the transverse component segments of the lightwave's trajectory through the waveguide are superimposed and thussubject to constructive or destructive interference. When the transversecomponent segments of the light wave interfere constructively(resonate), all points of the wavefront are in phase, and light is ableto propagate through the waveguide. The superimposition of thetransverse component segments results in a waveform such as thosedepicted in FIG. 4. However, when the transverse component segments ofthe light wave interfere destructively, light does not propagate.

The geometry of the waveguide, the angle of incidence, and the frequency(wavelength) of light affect the relative phase of each transversecomponent segment and thus determine whether interference along thetransverse component occurs constructively or destructively, and thuswhether light can propagate through the waveguide. Specifically, forconstructive interference to occur, the phase of each transversecomponent segment can only vary by +2πm, where m is any integer.

The number of allowed modes, and/or the geometric conditions under whichconstructive interference occurs and light propagates through asymmetric waveguide along a given coordinate may be expressed in termsof Equations 6 and 7:V=(dk ₀/2)(n ₁ ² −n ₂ ²)^(1/2)  Equation 6V _(m) =mπ/2  Equation 7

where V is a dimensionless parameter used to describe the number ofmodes in the waveguide, d is the distance between the sides of thewaveguide along the coordinate of propagation (e.g., d_(x) or d_(y) inthe channel waveguide of FIG. 1A, or d_(x) in the slab waveguide of FIG.1B), k₀ is the wavenumber of the light wave (e.g., 2π/λ), n₁ is therefractive index of the propagating material, n₂ is the refractive indexof any cladding and/or the surrounding material (e.g., air) along thetransverse surfaces of the waveguide (as shown in, e.g., FIG. 3 and FIG.11), V_(m) refers to a mode of the waveguide having an index m, and m isany integer greater than or equal to 1. The parameters n₁, n₂, and d aredetermined by the materials and dimensions used to construct thewaveguide, while k₀ is a property of the light injected into thewaveguide. These parameters collectively determine the dimensionlessparameter V, which sets the upper limit of V_(m) in Equation 7. A modeV_(m) is allowed when the quantity mπ/2 is less than V. When V_(m) islarger than V, the mode is not allowed in the waveguide, and lightcannot propagate within the waveguide at that mode. For example, whenthe quantity V=(dk₀/2)(n₁ ²−n₂ ²)^(1/2) is about π/2, only m=0 (thefundamental mode having 0 nodes) is allowed. When a waveguide has V=10,V₆=3π≈9.42, while V₇>10, and thus the waveguide allows 7 modes (V₀ toV₆), with modes corresponding to V₇ and above not allowed. From theseexamples, it can be seen that a larger number of modes can be supportedby increasing the values of d, k₀, and the difference between n₁ and n₂.

From another perspective, as the index of a mode increases, thefrequency with which the light wave bounces off the sides of thewaveguide increases, and the angle at which light bounces off the sidesof the waveguide decreases with respect to the normal. As discussedabove, when the angle of incidence is decreased to an angle smaller thanthe critical angle, light no longer undergoes TIR and is transmittedoutside of the waveguide. As such, at a large enough mode, the angle ofincidence becomes smaller than the critical angle and light is lost totransmission.

It will be understood that although Equations 6 and 7 herein refer topropagation within a symmetric two-dimensional (slab structure)waveguide, those having ordinary skill in the art are capable ofgeneralizing or deriving the equivalent equations for additional cases,including channel structure waveguides and waveguides in an asymmetricenvironment (e.g., having different materials as cladding on each side).

In some embodiments, the waveguide may be configured to support singlemode waveguiding behavior. The waveguide may have a channel structure ora slab structure. For example, n₁, n₂, and d of the waveguide and k₀ ofthe injected light may be selected so that only the fundamental mode isable to propagate within the waveguide. When a waveguide is asingle-mode waveguide, the thickness of the waveguide may be constrainedto the order of one or two wavelengths. Examples of waveguide materials,parameters, and light sources fulfilling these parameters are describedherein, and it will be understood that those having ordinary skill inthe art are capable of selecting suitable combinations of such materialsand light sources according to the examples and principles describedherein.

In some embodiments, the waveguide may be configured to supportmultimode waveguiding behavior. The waveguide may have a channelstructure or a slab structure. For example, n₁, n₂, and d of thewaveguide and k₀ of the injected light may be selected so that two ormore modes are able to propagate within the waveguide. Examples ofwaveguide materials, parameters, and light sources fulfilling theseparameters are described herein, and it will be understood that those ofskill in the art are capable of selecting suitable combinations of suchmaterials and light sources according to the examples and principlesdescribed herein.

In some embodiments, the self-sanitizing surface structure may include asingle waveguide having a slab structure. For example, the slabstructure waveguide may have a broad surface area sufficient to coverthe surface of interest.

In some embodiments, the self-sanitizing surface structure may include afirst waveguide and at least one additional waveguide adjacent to thefirst waveguide (e.g., two or more parallel and adjacent waveguides, oran array of waveguides); and parallel feeding optics or optics splittersto divide input UV light into the end of the propagating layer of eachwaveguide. In some embodiments, the self-sanitizing surface structuremay include an array of single-mode waveguides, for example, an array ofsingle-mode channel waveguides. Such an array may have the advantage ofallowing greater control over the propagation and distribution of lightin order to avoid local variations in the intensity of refracted light(e.g., hotspots and weak spots). When the self-sanitizing surfacestructure includes multiple parallel channel waveguides, the materialsfor each waveguide may be selected independently.

Aspects of embodiments of the present disclosure provide a method offabricating a self-sanitizing surface structure. The self-sanitizingsurface structure may be configured to selectively refract light (e.g.,only in the presence of a contaminating residue, as described herein).The method includes: attaching a waveguide to a substrate, the waveguideincluding a propagating layer; and coupling a UV light source to aninjection end of the propagating layer.

In some embodiments, the waveguide may further include a support layerbetween the propagating layer and the substrate. As such, the method offabricating a self-sanitizing surface structure may further includeattaching the support layer to a substrate. For example, the attachingthe support layer to a substrate may be carried out prior to attachingthe waveguide to the support layer, but embodiments of the presentdisclosure are not limited thereto.

In some embodiments, one or more components of the waveguide, includingthe propagating layer and the support layer, may be separately formedand subsequently attached to the substrate. For example, materials forforming the propagating layer and/or the support layer may be obtainedas layers, films, or foils that are cut or shaped into a suitable sizefor the substrate. The materials may be attached to the substrate usingany suitable method, as long as the bonding method does not interferewith propagation of light within the waveguide, for example, byabsorbing light or introducing a non-reflective interface on thewaveguide surface. For example, the propagating layer and the supportlayer may be attached to the substrate using an adhesive.

In some embodiments, one or more components of the waveguide, includingthe propagating layer and the support layer, may be formed in situ anddirectly on the substrate. For example, the attaching the waveguide to asubstrate may include depositing a suitable material for the supportlayer and/or the propagating layer on the substrate. When the waveguideincludes a propagating layer without a support layer, the propagatinglayer may be deposited directly on the substrate. When the waveguideincludes a support layer and a propagating layer, the support layer maybe deposited directly on the substrate, and the propagating layer may bedeposited directly on the support layer.

The method or techniques used to deposit the material for the supportlayer and/or the propagating layer are not particularly limited, and maybe selected according to the desired material and structure (e.g.,thickness) of each. In some embodiments, when the material for thesupport layer is a metal layer, the metal may be deposited by spraying,sputtering, spin coating, etc. In some embodiments, when the materialfor the support layer is a polymer having a lower refractive index thanthe propagating material, the polymer may be deposited by applying apre-polymer solution (e.g., a solution containing monomers andoligomers) to the substrate, and curing the coating. The depositing thepre-polymer solution may be accomplished via any suitable method,including spraying, spin-coating, dip coating, evaporation, etc. Thecuring may be accomplished using any suitable method, including heatingand UV-irradiation, depending on the type of polymer.

In some embodiments, when the material for the support is a layer ofair, supportive structures for suspending the propagating layer abovethe layer of air may be formed of any suitably supportive andnon-absorbing material such as metal, optically reflective PTFE, etc.,and may be attached to the substrate and the propagating layer using thesame methods described in connection with the separately formed layers.

In some embodiments, when the material for the propagating layer is aUV-transparent polymer or fluoropolymer, the polymer may be deposited byapplying a UV-transparent pre-polymer solution (e.g., a solutioncontaining monomers and oligomers) to the substrate, and curing thecoating. The depositing the UV-transparent pre-polymer solution may beaccomplished via any suitable method, including spraying, spin-coating,dip coating, evaporation, etc. The curing may be accomplished using anysuitable method, including heating and UV-irradiation, depending on thetype of polymer. The UV-transparent polymer or fluoropolymer produced bythe UV-transparent polymer may be the same as described herein inconnection with the self-sanitizing surface structure.

In some embodiments, the area for depositing the propagating layer maybe selected by using optical mirrors to define the sides of thepropagating layer, as well as to prevent or reduce light transmission atthe edges of the self-sanitizing surface structure. In some embodiments,the method may further include attaching optical mirrors to longitudinalsides of the substrate, the optical mirrors having a height larger thanthat of the substrate; and depositing the suitable material for thepropagating layer on the substrate between the optical mirrors. In otherembodiments, the method may include attaching the optical mirrors to theupper surface of the substrate at positions that define the outer area(e.g., one or more longitudinal sides) of the propagating layer. Inother embodiments, the area for depositing the propagating layer may beselected using, for example, a deposition mask, and optical mirrors maybe subsequently attached to the sides of the propagating layer using anysuitable technique, as described above.

In some embodiments, the method of fabricating a self-sanitizing surfacestructure may further include depositing a metal layer on thepropagating layer, the metal layer being configured to generate surfaceplasmon polaritons (SPPs). The metal layer may be the same as describedherein in connection with the self-sanitizing surface structure.

The properties and materials of the substrate, optical mirrors,propagating layer, support layer, UV light source, and metal layer mayeach be the same as described herein with respect to the self-sanitizingsurface structure, but embodiments of the present disclosure are notlimited thereto.

In some embodiments, the self-sanitizing surface structure may befabricated as an array of two or more adjacent and/or parallel surfaces.Each of the adjacent and/or parallel surfaces may be deposited usingsimilar materials, methods, and parameters as described above for thesingle surface. The array of surfaces may be deposited simultaneously orsuccessively.

In some embodiments, the method of fabricating a self-sanitizing surfacestructure may include attaching optical mirrors to longitudinal sides ofa substrate, the optical mirrors having a height larger than that of thesubstrate; forming the support layer on the substrate between theoptical mirrors; forming the propagating layer by applying anultraviolet (UV)-transparent pre-polymer coating on the support layerbetween the optical mirrors and curing the UV-transparent pre-polymercoating; and coupling a UV light source to an injection end of thepropagating layer.

FIG. 12 is a schematic diagram showing a self-sanitizing surfacestructure 220 including a UV lamp 221, a focusing lens 223, and aterminal end mirror 231 as optical components, and a multi-layerstructure including a substrate layer 225, a support layer 227 on thesubstrate layer 225, and a propagating layer 229 on the substrate layer225. UV light 241 is produced by the UV lamp 221, passed through thelens 223, and injected into the propagating layer 229 within theinjection angle 243, such that a portion of the light 247 is refractedin the presence of a residue 235, and the remaining portion 245 remainswithin the propagating layer 229. Each layer of the multi-layerstructure may be the same as described herein, according to embodimentsof the present disclosure.

Aspects of embodiments of the present disclosure provide a method ofdecontaminating or reducing contamination on a self-sanitizing surfacestructure, the self-sanitizing surface structure including a waveguide,and the waveguide including a propagating layer and a support layer thatis structured and fabricated according to the methods described herein.The method may include: selecting a wavelength of UV light and a lightinjection angle; selecting a material for a propagating layer and amaterial for a support layer; assembling the self-sanitizing surfacestructure from the selected material for the propagating layer and theselected material for the support layer to form a waveguide; andinjecting UV light into the propagating layer at the light injectionangle to selectively refract light from a transverse side of thewaveguide in the self-sanitizing surface structure.

FIG. 13 is a flowchart or block diagram 250 summarizing the factors andacts included in the method of decontaminating or reducing contaminationon a self-sanitizing surface structure utilizing selectively refractedlight. Although the acts of selection (251) described herein are listedsequentially, they are not necessarily carried out sequentially or inthe recited order; rather, they reflect the simultaneous determinationand selection of a combination of parameters, such as those associatedwith selecting the UV light wavelength and injection angle (253),propagating layer material (255), and support layer material (257), someof which may be constrained by outside factors. Once the parameters havebeen determined in tandem, the self-sanitizing surface structure isassembled (259), and UV light may be injected into the propagating layer(261).

For example, the wavelength of UV light may be selected (253) byconsidering the range or specific wavelengths of light produced by a UVlight source; the wavelength of light necessary to destroy the residueson the self-sanitizing surface structure; the transparency of thepropagating layer to the wavelength of light; the allowable modes of thewaveguide, etc., as described above.

The material included in the propagating layer and the thickness of thepropagating layer may be suitably selected (255) by considering thetransparency of the layer to the wavelength of light necessary todestroy the residues on the self-sanitizing surface structure; therefractive index of the material in relation to the refractive indexesof air, the residue, and the support layer; the desired number of modesin the waveguide (e.g., single mode or multi-mode), ease of deposition,material costs; durability, etc.

The material included in the support layer may be suitably selected(257) by considering the refractive index of the material in relation tothe refractive indexes of the propagating layer, residue, and air; easeof deposition, material costs, etc.

The light injection angle may be suitably selected by considering therefractive indexes of the propagating layer, environment, support layer,and residue; the angle of incidence necessary for total reflection tooccur, the available modes of the waveguide, etc. As described above,the light should be injected at an angle such that it undergoes TIRunder clean conditions, but is refracted in the presence of a residue.The light injection angle may be adjusted using the optics couplingcomponents described herein, include collimating optics, mirrors,refractive lenses, reflective lenses, optical fibers, prisms orgratings, and it will be understood that those having ordinary skill inthe art are capable of suitably configuring such components to arrive atthe desired light injection angle and to achieve the injecting of UVlight into the propagating layer.

The assembling the self-sanitizing surface structure (259) and theinjecting UV light into the propagating layer at a suitable lightinjection angle (261) may be the same as described herein with respectto the self-sanitizing surface structure and the method of fabricating aself-sanitizing surface structure. In some embodiments, the assemblingthe self-sanitizing surface structure may further include attachingoptical components, mirrors, etc., as described herein.

Typical devices including fiber optic cables and other types or kinds ofwaveguides in the related art have used such waveguides to transmitlight from one end of the waveguide to the other (e.g., along the fulllength of the waveguide). Light is injected into the propagatingmaterial via direct contact with a light source at a first end of thewaveguide. The waveguide is typically designed or selected (for example,through the use of cladding) so that substantially no light is refractedalong the length of the waveguide at all times, e.g. under the range ofnormal operating conditions. The light thus travels to the opposite endof the waveguide, which may be positioned at or over a desiredirradiation target, and is refracted only at that boundary. Changes inthe environment along the sides of the waveguide typically do not resultin light emission or other optical changes, and/or the waveguides aredesigned to be unresponsive to such changes. As such, UV light passingthrough such waveguides in the related art enter and exit the waveguidethough longitudinal sides (or ends) of the waveguide, and the exit siteof the light typically remains fixed.

In contrast, embodiments of the present disclosure are designed orconfigured so that selective refraction from one or more points alongthe sides of the waveguide is possible, and sometimes encouraged, underspecific conditions (e.g., in the presence of a residue). Further,embodiments of the present disclosure may be designed or selected sothat refraction along the surface structure can be automatically toggledon or off in response to environmental changes, without requiringadditional user input such as physical repositioning of the waveguide,recalculating a suitable input, or even flipping a switch. As such, UVlight passing through self-sanitizing surface structures according toembodiments of the present disclosure may enter and exit the waveguidethough longitudinal sides (or ends) of the waveguide under one set ofconditions (e.g., in the absence of a residue), but the exit site of thelight may be subsequently located on a transverse side of the waveguideunder a second set of conditions (e.g., when a residue is on thetransverse side of the waveguide).

Furthermore, embodiments of the present disclosure may be designed orconfigured as described herein so that refraction does not occurindiscriminately and uniformly across the entire area covered by theself-sanitizing surface structure, but instead occurs only underspecific, controlled conditions and with spatial selectivity (e.g., inregions of the waveguide that are in direct contact with a residue viaselective refraction, as described in detail herein), thereby reducingthe risk of inappropriate light exposure.

In addition, other types or kinds of devices utilizing UV light forsanitation purposes have typically applied the light to surfaces bymanually holding or permanently positioning an external UV light sourceover the surface or item to be sanitized, which can be bulky andinconvenient. Further, such UV light sources are often high power inorder to generate sufficient light flux for sanitization. In contrast,embodiments of the present disclosure may provide a permanentself-sanitizing fixture with reduced power requirements compared toconventional methods using an external UV light source.

The following example embodiments are provided solely to aid inunderstanding of the invention, and are not intended to be limiting inany form.

EXAMPLES Example 1

A self-sanitizing surface structure configured to selectively emit lightis formed by placing a support layer formed of Ag coated Mylar on astructural layer. A propagating layer formed of PCTFE (n=1.435) isthermally bonded to the support. Subsequently, mirrored Al pieces areattached to the longitudinal sides of the support layer and propagatinglayer. A UV light source including a Hg vapor lamp (UV-C emission at 184nm and 254 nm) is placed in a mirrored container with an opening matedto a prism that is heat bonded to the PCTFE surface, thereby completingmanufacture of a self-sanitizing surface structure.

When the self-sanitizing surface structure of Example 1 is used in air,the critical angle is 44.2°. When the self-sanitizing surface structureis exposed to a residue including water, the critical angle at the pointof contamination is 67.9°. Therefore, UV light from the Hg vapor lampwas injected into the propagating layer at an incident angle between44.2° to 67.9° in order to achieve TIR in clean regions andrefraction-aided sanitization in the contaminated region.

Example embodiments of the present disclosure may be suitably used inenvironments that are frequently exposed to pathogens, are prone tocross-contamination, or may be vulnerable to chemical and biologicalweapon attack, including lavatories, bathrooms, hospitals, seating areasin publically used or shared vehicles, military bases, ambulances,laboratories, and food preparation facilities.

Example embodiments of the present disclosure may be suitably applied toa wide range of surfaces and surface types, including walls, floors,ceilings, fixtures (such as desks, counters, benches, equipmentcabinets, fume hoods, and biological hoods), and portable equipment(such as gurneys and chairs). Further, example embodiments of thepresent disclosure may be used to disinfect objects pressed against thesurface (such as gloves, shoes, clothing, hands, tools, etc.), or may beincorporated into a portable surface that can be pressed against otherobjects and surfaces, such as those described above.

FIGS. 14A-B depict example rooms and surfaces to which self-sanitizingsurface structures according to embodiments of the present disclosuremay be applied. It will be understood that these images are providedmerely for illustration, and do not limit the intended applications orforms of embodiments of the present disclosure. In FIG. 14A, any fixedstructural surface of a room or building, including the floors 301,walls 303, ceiling 305, windows 307, etc., may be modified to includeself-sanitizing surface structures according to embodiments of thepresent disclosure. Furthermore, the surfaces of movable furnitureitems, including chairs 311, desks 313, benches 315, and countertops 317may also modified to include self-sanitizing surface structuresaccording to embodiments of the present disclosure. In FIG. 14B,depicting a public lavatory 330, any structural surface including thefloors 331, walls 333, ceiling 335, etc., may be modified to includeself-sanitizing surface structures according to embodiments of thepresent disclosure. Furthermore, any utility surfaces including thetoilet 339, countertop 441, cabinet doors 443, trash receptacle door 445(including its handle), and wash basin 447, may also modified to includeself-sanitizing surface structures according to embodiments of thepresent disclosure. As can be observed from the toilet 339 and washbasin 447, the surfaces modified to include a self-sanitizing surfacestructures may be planar or may be curved. Indeed, self-sanitizingsurface structures according to embodiments of the present disclosuremay be widely applied to various human-built environments and objects asa versatile and safe means of surface sanitization.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. As used herein, the terms “substantially”, “about”, “nearly”,and similar terms are used as terms of approximation and not as terms ofdegree, and are intended to account for the inherent deviations inmeasured or calculated values that would be recognized by those ofordinary skill in the art. Plural encompasses singular and vice versa.For example, while the present disclosure may describe “an” oligomer or“a” photopolymer, a mixture of such oligomers or photopolymers can beused. Also, any numerical range recited herein is intended to includeall sub-ranges of the same numerical precision subsumed within therecited range. For example, a range of “1.0 to 10.0” is intended toinclude all subranges between (and including) the recited minimum valueof 1.0 and the recited maximum value of 10.0, that is, having a minimumvalue equal to or greater than 1.0 and a maximum value equal to or lessthan 10.0, such as, for example, 2.4 to 7.6. Any maximum numericallimitation recited herein is intended to include all lower numericallimitations subsumed therein and any minimum numerical limitationrecited in this specification is intended to include all highernumerical limitations subsumed therein. Accordingly, Applicant reservesthe right to amend this specification, including the claims, toexpressly recite any sub-range subsumed within the ranges expresslyrecited herein. As used herein, the terms “combination thereof” and“combinations thereof” may refer to a chemical combination (e.g., analloy or chemical compound), a mixture, or a laminated structure ofcomponents.

It will be understood that although the terms “first”, “second”,“third”, etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, a first element, component, region, layer or sectiondescribed below could be termed a second element, component, region,layer or section, without departing from the spirit and scope of thepresent disclosure.

Spatially relative terms, such as “beneath”, “below”, “lower”, “under”,“above”, “upper”, and the like, may be used herein for ease ofexplanation to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the accompanying drawings. Itwill be understood that the spatially relative terms are intended toencompass different orientations of the device in use or in operation,in addition to the orientations depicted in the accompanying drawings.For example, if the structures in the accompanying drawings are turnedover, elements described as “below” or “beneath” or “under” otherelements or features would then be oriented “above” the other elementsor features. Thus, the example terms “below” and “under” can encompassboth an orientation of above and below. The device may be otherwiseoriented (e.g., rotated 90 degrees or at other orientations) and thespatially relative descriptors used herein should be interpretedaccordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a” and “an” are intendedto include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes”, and “including”, when used inthis specification, specify the presence of the stated features,integers, acts, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, acts, operations, elements, components, and/or groups thereof.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of”, when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.Further, the use of “may” when describing embodiments of the inventiveconcept refers to “one or more embodiments of the inventive concept.” Asused herein, the terms “use,” “using,” and “used” may be consideredsynonymous with the terms “utilize,” “utilizing,” and “utilized,”respectively.

While the subject matter of the present disclosure has been described inconnection with certain embodiments, it is to be understood that thesubject matter of the present disclosure is not limited to the disclosedembodiments, but, on the contrary, the present disclosure is intended tocover various modifications and equivalent arrangements included withinthe spirit and scope of the appended claims, and equivalents thereof.

What is claimed is:
 1. A self-sanitizing surface structure, theself-sanitizing surface structure comprising a waveguide; the waveguidecomprising: a propagating layer having a first transverse side and asecond transverse side opposite the first transverse side, the firsttransverse side being exposed to air and configured to selectivelyrefract light; and a support layer in direct contact with the secondtransverse side of the propagating layer and between the propagatinglayer and a substrate covered by the self-sanitizing surface structure,the support layer comprising: one or more spacers being of a materialthat does not absorb or transmit light; and air surrounding the one ormore spacers; and the waveguide being configured to selectively refractabout 0.01% to about 25% of the flux of an ultraviolet (UV) lightinjected into the propagating layer, the selective refraction occurringwhen a residue is on the first transverse side and at an interfacebetween the first transverse side and the residue.
 2. Theself-sanitizing surface structure of claim 1, wherein the propagatinglayer is formed of amorphous silica, quartz, a metal fluoride, afluoropolymer, a cyclic ether-containing fluoropolymer, aPTFE-terpolymer, polychlorotrifluoroethylene (PCTFE), a cyclic olefincopolymer (COC), polymethylpentene, or zinc sulfide.
 3. Theself-sanitizing surface structure of claim 1, wherein the propagatinglayer has a refractive index of about 1.3 to about 2.5.
 4. Theself-sanitizing surface structure of claim 1, wherein the spacerscomprise a mirror or metallic layer.
 5. The self-sanitizing surfacestructure of claim 1, wherein the spacers have a lower refractive indexthan the propagating layer.
 6. The self-sanitizing surface structure ofclaim 1, wherein the spacers comprise porous silica.
 7. Theself-sanitizing surface structure of claim 1, further comprising: anultraviolet (UV) light source for generating UV light; and optics todirect the UV light into the propagating layer, the optics beingdirectly coupled to an end of the propagating layer perpendicular to thefirst and second transverse sides.
 8. The self-sanitizing surfacestructure of claim 7, wherein the UV light source is an excimer lamp, adownshifting excimer lamp, an excimer laser, a light emitting diode(LED), a mercury (Hg) vapor lamp, or a light source comprising AlGaNquantum wells.
 9. The self-sanitizing surface structure of claim 7,wherein the UV light source generates UV-C light.
 10. Theself-sanitizing surface structure of claim 7, wherein the opticscomprise collimating optics, mirrors, refractive or reflective lenses,metamaterial-based lenses, Fresnel lenses, fibers, standard single modeoptical fibers, multimode optical fibers, photonic crystal opticalfibers, or a combination thereof.
 11. The self-sanitizing surfacestructure of claim 7, wherein the optics are coupled to the end of thepropagating layer via a prism or grating.
 12. The self-sanitizingsurface structure of claim 1, wherein the propagating layer does notinclude any germicidal coating or layer on the first transverse side.13. The self-sanitizing surface structure of claim 1, further comprisinga metal coating on the first transverse side of the propagating layer,the metal coating being configured to convert ultraviolet (UV)-C photonsto surface plasmon polaritons (SPPs).
 14. The self-sanitizing surfacestructure of claim 1, further comprising an optical mirror on aterminating longitudinal side of the propagating layer.
 15. Theself-sanitizing surface structure of claim 1, further comprising astructural layer under the support layer.
 16. The self-sanitizingsurface structure of claim 1, wherein the waveguide is configured tosupport multimode waveguiding behavior.
 17. The self-sanitizing surfacestructure of claim 1, wherein the residue comprises an organic compound,a microorganism, or a nucleic acid.
 18. The self-sanitizing surfacestructure of claim 7, further comprising: an additional waveguidepositioned surface-adjacent to the waveguide, the additional waveguideincluding a propagating layer; and parallel feeding optics or opticssplitters to divide and inject the UV light into the propagating layersof the waveguide and the additional waveguide.